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  • 51.
    Keller, Jan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Stolt, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Törndahl, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Atomic layer deposition of In2O3 transparent conductive oxide layers for application in Cu(In,Ga)Se2 solar cells with different buffer layers2016In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 213, no 6, p. 1541-1552Article in journal (Refereed)
    Abstract [en]

    This contribution presents the development of atomic layer deposited (ALD) In2O3 films for utilization as transparent conductive oxide (TCO) layers in Cu(In,Ga)Se2 (CIGSe) solar cells. The effects of ALD process parameters on the morphology and growth of In2O3 are studied and related to the electrical and optical properties of the films. Maintaining similar resistivity values compared to commonly used ZnO:Al (AZO) TCOs (ρ = (5–7) × 10−4 Ωcm), a superior mobility of μ ≈ 110 cm2/Vs could be achieved (more than five times higher than a ZnO:Al reference), which results in a significantly reduced parasitic optical absorption in the infrared region. Application of the optimized In2O3 layers in CIGSe solar cells with varying buffer layers (CdS and Zn1–xSnxOy (ZTO)) leads to a distinct improvement in short circuit current density Jsc in both cases. While for solar cells containing the ZTO/In2O3 window structure, a drop in open-circuit voltage Voc and a deterioration under illumination is observed, the TCO exchange (from AZO to In2O3) on CdS buffer layers results in an increase in Voc without detectable light bias degradation. The efficiency η of the best corresponding solar cells could be improved by about 1% absolute.

  • 52.
    Kotipalli, R.
    et al.
    Catholic Univ Louvain, ICTEAM, B-1348 Louvain La Neuve, Belgium..
    Vermang, Bart
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Univ Louvain, ESAT KU Leuven, B-3001 Louvain, Belgium.;IMEC, B-3001 Louvain, Belgium..
    Joel, J.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Rajkumar, R.
    Catholic Univ Louvain, ICTEAM, B-1348 Louvain La Neuve, Belgium..
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Flandre, D.
    Catholic Univ Louvain, ICTEAM, B-1348 Louvain La Neuve, Belgium..
    Investigating the electronic properties of Al2O3/Cu(In, Ga)Se-2 interface2015In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 5, no 10, article id 107101Article in journal (Refereed)
    Abstract [en]

    Atomic layer deposited (ALD) Al2O3 films on Cu(In, Ga)Se-2 (CIGS) surfaces have been demonstrated to exhibit excellent surface passivation properties, which is advantageous in reducing recombination losses at the rear metal contact of CIGS thin-film solar cells. Here, we report, for the first time, experimentally extracted electronic parameters, i.e. fixed charge density (Q(f)) and interface-trap charge density (D-it), for as-deposited (AD) and post-deposition annealed (PDA) ALD Al2O3 films on CIGS surfaces using capacitance-voltage (C-V) and conductance-frequency (G-f) measurements. These results indicate that the AD films exhibit positive fixed charges Q(f) (approximately 10(12) cm(-2)), whereas the PDA films exhibit a very high density of negative fixed charges Q(f) (approximately 10(13) cm(-2)). The extracted D-it values, which reflect the extent of chemical passivation, were found to be in a similar range of order (approximately 10(12) cm(-2) eV(-1)) for both AD and PDA samples. The high density of negative Q(f) in the bulk of the PDA Al2O3 film exerts a strong Coulomb repulsive force on the underlying CIGS minority carriers (n(s)), preventing them to recombine at the CIGS/Al2O3 interface. Using experimentally extracted Q(f) and D-it values, SCAPS simulation results showed that the surface concentration of minority carriers (n(s)) in the PDA films was approximately eight-orders of magnitude lower than in the AD films. The electrical characterization and estimations presented in this letter construct a comprehensive picture of the interfacial physics involved at the Al2O3/CIGS interface. (C) 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

  • 53. Kotipalli, Ratan
    et al.
    Vermang, Bart
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Fjällström, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Delamare, Romain
    Flandre, Denis
    Influence of Ga/(Ga plus In) grading on deep-defect states of Cu(In, Ga)Se-2 solar cells2015In: Physica Status Solidi. Rapid Research Letters, ISSN 1862-6254, E-ISSN 1862-6270, Vol. 9, no 3, p. 157-160Article in journal (Refereed)
    Abstract [en]

    The benefits of gallium (Ga) grading on Cu(In, Ga) Se-2 (CIGS) solar cell performance are demonstrated by comparing with ungraded CIGS cells. Using drive-level capacitance profiling (DLCP) and admittance spectroscopy (AS) analyses, we show the influence of Ga grading on the spatial variation of deep defects, free-carrier densities in the CIGS absorber, and their impact on the cell's open-circuit voltage V-oc. The parameter most constraining the cell's Voc is found to be the deep-defect density close to the space charge region (SCR ). In ungraded devices, high deep-defect concentrations (4.2 x 1016 cm(-3)) were observed near the SCR, offering a source for Shockley Read-Hall recombination, reducing the cell's Voc. In graded devices, the deep-defect densities near the SCR decreased by one order of magnitude (2.5 x 1015 cm(-3)) for back surface graded devices, and almost two orders of magnitude (8.6 x 1014 cm(-3)) for double surface graded devices, enhancing the cell's Voc. In compositionally graded devices, the free-carrier density in the absorber's bulk decreased in tandem with the ratio of gallium to gallium plus indium ratio GGI = Ga/(Ga + In), increasing the activation energy, hindering the ionization of the defect states at room temperature and enhancing their role as recombination centers within the energy band.

  • 54.
    Kubart, Tomas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ericson, Tove
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Scragg, Jonathan J.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Platzer-Bjorkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Reactive sputtering of Cu2ZnSnS4 thin films - Target effects on the deposition process stability2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 240, p. 281-285Article in journal (Refereed)
    Abstract [en]

    Cu2ZnSnS4 (TS) is a promising material for thin film solar cells which contains only abundant elements. This work focuses on the stability of elemental composition of films deposited by reactive sputtering of CuSn alloy targets in H2S. Long equilibration times of several hours were observed. The main reason is the formation of a thick Cu2S layer on the target surface. Especially in areas with low erosion rate, the Cu2S thickness reaches up to 700 pm and is accompanied by a preferential loss of Sn from the target. Based on the results, it is suggested that the formation of Cu2S may be limited either by more uniform erosion of the target surface or by reduction of the H2S partial pressure.

  • 55.
    Larsson, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Keller, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Törndahl, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Evaluation of different intrinsic ZnO and transparent conducting oxide layer combinations in Cu(In,Ga)Se2 solar cells2017In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 633, p. 235-238Article in journal (Refereed)
    Abstract [en]

    We studied the interaction of four different window layer combinations in Cu(In,Ga)Se-2 solar cells. Intrinsic ZnO (i-ZnO) layers were grown on CdS by either chemical vapor deposition (CVD) or magnetron sputtering. These were combined with sputtered ZnO:Al or In2O3:H grown by atomic layer deposition as transparent conducting oxides (TCO). It was found that the thickness of the CVD i-ZnO layer affects the open circuit voltage (V-oc) significantly when using In2O3:H as TCO. The V-oc dropped by roughly 30 mV when the i-ZnO thickness was increased from 20 to 160 nm. This detrimental effect on V-oc was not as prominent when a ZnO:Al TCO was used, where the corresponding decrease was in the range of 5 to 10 my. In addition, the V-oc drop for the CVD i-ZnO/In2O3:H structure was not observed when using the sputtered i-ZnO layer. Furthermore, large fill factor variations were observed when using the In2O3:H TCO without an i-ZnO layer underneath, where already a thin (20 nm) CVD i-ZnO layer mitigated this effect. Device simulations were applied to explain the experimentally observed Voc trends.

  • 56.
    Ledinek, Dorothea
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Salome, Pedro
    Int Iberian Nanotechnol Lab, Braga, Portugal; Univ Aveiro, Dept Phys, Aveiro, Portugal.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zimmermann, Uwe
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Rear Contact Passivation for High Bandgap Cu(In, Ga)Se2 Solar Cells With a Flat Ga profile2018In: IEEE Journal of Photovoltaics, ISSN 2156-3381, E-ISSN 2156-3403, Vol. 8, no 3, p. 864-870Article in journal (Refereed)
    Abstract [en]

    In this study, Cu(In, Ga)Se2 solar cells with a high bandgap (1.31 eV) and a flat Ga profile ([Ga]/([Ga]+[In]) ≈ 0.60) were examined. For absorber layer thicknesses varying from 0.60 to 1.45 μm, the Mo rear contact of one set of samples was passivated with an ultrathin (27 nm) Al2O3 layer with point contact openings, and compared with reference samples where the rear contact remained unpassivated. For the passivated samples, mainly large gains in the short-circuit current led to an up to 21% (relative) higher power conversion efficiency compared with unpassivated cells. The differences in temperature-dependent current voltage behavior between the passivated and the unpassivated samples and the thin and the thick samples can be explained by an oppositely poled secondary photodiode at the rear contact.

  • 57.
    Lindahl, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Wätjen, J. Timo
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Törndahl, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    The effect of substrate temperature on atomic layer deposited zinc tin oxide2015In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 586, p. 82-87Article in journal (Refereed)
    Abstract [en]

    Zinc tin oxide (ZTO) thin films were deposited on glass substrates by atomic layer deposition (ALD), and the film properties were investigated for varying deposition temperatures in the range of 90 to 180 degrees C. It was found that the [Sn]/([Sn] + [Zn]) composition is only slightly temperature dependent, while properties such as growth rate, film density, material structure and band gap are more strongly affected. The growth rate dependence on deposition temperature varies with the relative number of zinc or tin containing precursor pulses and it correlates with the growth rate behavior of pure ZnO and SnOx ALD. In contrast to the pure ZnO phase, the density of the mixed ZTO films is found to depend on the deposition temperature and it increases linearly with about 1 g/cm(3) in total over the investigated range. Characterization by transmission electron microscopy suggests that zinc rich ZTO films contain small (similar to 10 nm) ZnO or ZnO(Sn) crystallites embedded in an amorphous matrix, and that these crystallites increase in size with increasing zinc content and deposition temperature. These crystallites are small enough for quantum confinement effects to reduce the optical band gap of the ZTO films as they grow in size with increasing deposition temperature.

  • 58.
    Lindahl, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Keller, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Donzel-Gargand, Olivier
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Szaniawski, Piotr
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Törndahl, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Deposition temperature induced conduction band changes in zinc tin oxide buffer layers for Cu(In,Ga)Se2 solar cells2016In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 144, p. 684-690Article in journal (Refereed)
    Abstract [en]

    Thin film Cu(In,Ga)Se2 solar cells with ALD-deposited Zn1-xSnxOy buffer layers were fabricated and the solar cell properties were investigated for varying ALD deposition temperatures in the range from 90 °C up to 180 °C. It was found that a process window exists between 105 °C and 135 °C, where high solar cell efficiency can be achieved. At lower ALD deposition temperatures the solar cell performance was mainly limited by low fill factor and at higher temperatures by low open circuit voltage. Numerical simulations and electrical characterization were used to relate the changes in solar cell performance as a function of ALD deposition temperature to changes in the conduction band energy level of the Zn1-xSnxOy buffer layer. The Zn1-xSnxOy films contain small ZnO or ZnO(Sn) crystallites (~10 nm), resulting in quantum confinement effects influencing the optical band gap of the buffer layer. The ALD deposition temperature affects the size of these crystallites and it is concluded that most of the changes in the band gap occur in the conduction band level.

  • 59.
    Lindahl, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Wätjen, Jörn Timo
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hultqvist, Adam
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ericson, Tove
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Törndahl, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    The effect of Zn1−xSnxOy buffer layer thickness in 18.0% efficient Cd-free Cu(In,Ga)Se2 solar cells2013In: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 21, no 8, p. 1588-1597Article in journal (Refereed)
    Abstract [en]

    The influence of the thickness of atomic layer deposited Zn1−xSnxOy buffer layers and the presence of an intrinsic ZnO layer on the performance of Cu(In,Ga)Se2 solar cells are investigated. The amorphous Zn1−xSnxOy layer, with a [Sn]/([Sn] + [Zn]) composition of approximately 0.18, forms a conformal and in-depth uniform layer with an optical band gap of 3.3 eV. The short circuit current for cells with a Zn1−xSnxOy layer are found to be higher than the short circuit current for CdS buffer reference cells and thickness independent. On the contrary, both the open circuit voltage and the fill factor values obtained are lower than the references and are thickness dependent. A high conversion efficiency of 18.0%, which is comparable with CdS references, is attained for a cell with a Zn1−xSnxOy layer thickness of approximately 13 nm and with an i-ZnO layer.

  • 60.
    Lindahl, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zimmermann, Uwe
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Szaniawski, Piotr
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Törndahl, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hultqvist, Adam
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Salomé, Pedro
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Platzer-Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Inline Cu(In,Ga)Se-2 Co-evaporation for High-Efficiency Solar Cells and Modules2013In: IEEE JOURNAL OF PHOTOVOLTAICS, ISSN 2156-3381, Vol. 3, no 3, p. 1100-1105Article in journal (Refereed)
    Abstract [en]

    In this paper, co-evaporation of Cu(In,Ga)Se-2 (CIGS) in an inline single-stage process is used to fabricate solar cell devices with up to 18.6% conversion efficiency using a CdS buffer layer and 18.2% using a Zn1-xSnxOy Cd-free buffer layer. Furthermore, a 15.6-cm(2) mini-module, with 16.8% conversion efficiency, has been made with the same layer structure as the CdS baseline cells, showing that the uniformity is excellent. The cell results have been externally verified. The CIGS process is described in detail, and material characterization methods show that the CIGS layer exhibits a linear grading in the [Ga]/([Ga]+[In]) ratio, with an average [Ga]/([Ga]+[In]) value of 0.45. Standard processes for CdS as well as Cd-free alternative buffer layers are evaluated, and descriptions of the baseline process for the preparation of all other steps in the Angstrom Solar Center standard solar cell are given.

  • 61.
    Lundberg, Olle
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Edoff, Marika Edoff
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Stolt, Lars
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Optimized growth conditions for Cu(In,Ga)Se2 layers by co-evaporation at high deposition rates2003In: Material Research Conference, Spring 2003, San Francisco, USA, 2003Conference paper (Refereed)
  • 62.
    Lundberg, Olle
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Edoff, Marika
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Stolt, Lars
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    The effect of Ga-grading in CIGS thin film solar cells2005In: Thin Solid Films, Vol. 480-481, p. 520-525Article in journal (Refereed)
  • 63.
    Lundberg, Olle
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Materials Science. Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Lu, Jun
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Materials Science. Department of Engineering Sciences, Electronics. Fasta tillståndets fysik.
    Rockett, Angus
    Edoff, M
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Materials Science. Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Stolt, Lars
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Materials Science. Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Diffusion of indium and gallium in Cu(In,Ga)Se2 thin film solar cells2002In: Proceedings of the International Conference on Ternary and Multinary Compounds, Paris, France, October, 2002Conference paper (Refereed)
  • 64.
    Lundberg, Olle
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Lu, Jun
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Analytisk materialfysik.
    Rockett, Angus
    Edoff, Marika
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Stolt, Lars
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Diffusion of indium and gallium in Cu(In,Ga)Se2 thin film solar cells2003In: Journal of physics and chemistry of solids, Vol. 64, p. 1499-1504Article in journal (Refereed)
  • 65.
    Malm, Ulf
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Fasta tillståndets elektronik.
    Carlsson, T
    Edoff, M
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Fasta tillståndets elektronik.
    Stability in Cu(In,Ga)Se2 solar cells with EVA encapsulation in varying damp heat conditions2006Conference paper (Refereed)
  • 66.
    Malm, Ulf
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Carlsson, Thomas
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Stability in Cu(In,Ga)Se2 Solar Cells with EVA Encapsulation in Varying Damp Heat Conditions2006In: Proceedings of the 21st European Photovoltaic Solar Energy Conference, Dresden, p. 1990-1993Article in journal (Refereed)
  • 67.
    Malm, Ulf
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    2-D device modelling and finite element simulations for thin-film solar cells2007Conference paper (Refereed)
  • 68.
    Malm, Ulf
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    2D Device modelling and finite element simulations for thin-film solar cells2009In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 93, no 6-7, p. 1066-1069Article in journal (Refereed)
    Abstract [en]

    Thin-film heterojunction solar cell devices are modelled in two dimensions, from fundamental material parameters, using the finite element method. The electrostatic potential is solved for, together with the quasi-Fermi levels, while optical absorption is calculated from n and k values of the materials used.In this implementation, all material parameters can be input as functions of spatial coordinates, which makes it very flexible when applied to materials with inhomogeneities. As an example of the model model in use, it is applied to a thin-film solar cell based on a structure with a CIGS absorber layer, a CdS buffer layer and a ZnO/ZAO transparent front contact. The effects of spatial inhomogeneities in the band gap energy and in the mid-gap trap level density on device performance are simulated.

  • 69.
    Malm, Ulf
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Influence from front contact sheet resistance on extracted diode parameters in CIGS solar cells2008In: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 16, no 2, p. 113-121Article in journal (Refereed)
    Abstract [en]

    The extraction of one-diode model parameters from a current-voltage (J-V) curve is problematic, since the model is one-dimensional while real devices are indeed three-dimensional. The parameters obtained by fitting the model curve to experimental data depend on how the current is collected, and more specifically the geometry of the contact. This is due to the non-uniform lateral current flow in the window layers, which leads to different parts of the device experiencing different front contact voltage drop, and hence different operating points on the ideal J-V curve. In this work, finite element simulations of three-dimensional contact structures are performed and compared to experimental data on Cu(In,Ga)Se2-based solar cell devices. It is concluded that the lateral current flow can influence the extracted parameters from the one-diode model significantly if the resistivity of the front contact material is high, or if there is no current collecting grid structure. These types of situations may appear in damp heat-treated cells and module type cells, respectively.

  • 70.
    Malm, Ulf
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Simulating Material Inhomogeneities and Defects in CIGS Thin-film Solar Cells2009In: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 17, no 5, p. 306-314Article in journal (Refereed)
    Abstract [en]

    Thin-film CIGS solar cells are simulated using a hybrid model   consisting of a distributed form of the analytical one diode model   paired with a numerical finite element model of the d.c. conduction in   the front contact layers. Variations in material quality over the   substrate surface., from measured J-V curves, are incorporated into the   model and the effects of cell width and window layer thickness are evaluated for homogeneous and inhomogeneous material quality. Furthermore, the effects of discrete shunt defects of different sizes   are modelled, and in different positions on the cell surface. The  results from optimizing cell width and window layer thickness show that   the effects of material inhomogeneities include a small shift of the   optimal parameters together with a less pronounced maximum. As   expected, the defect size is important to the shunt conductance   parameter of the resulting J-V curves. The passivating effect of the highly resistive ZnO layer is confirmed.

  • 71.
    Malm, Ulf
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Edoff, Marika
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Stolt, Lars
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    The Stability in Damp Heat Conditions of Thin-film CIGS Solar Cells with Different Absorber Thickness2004In: 19th European Photovoltaic Energy Conference, 7-11 June, Paris, France, 2004, p. 1890-1893Conference paper (Other scientific)
  • 72.
    Malmström, Jonas
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Kessler, John
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Edoff, Marika
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Stolt, Lars
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Electronics. Fasta tillståndets elektronik.
    Relation between composition and optical properties of CdS films grown by chemical bath deposition2004In: Proceedings 19th European Photovoltaic Solar Energy Conference (WIP-Münich, Münich, Vol II, 2004, p. 1909-1912Conference paper (Other scientific)
  • 73. Nsimama, P D
    et al.
    Samiji, M E
    Mbise, G W
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wennerberg, J
    Edoff, M
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Performance comparison of Cu(In,Ga)Se2 solar cells fabricated using RF and DC sputtered ZnO:Al transparent conducting oxides2008In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 5, no 2, p. 612-615Article in journal (Refereed)
  • 74. Nsimama, P. D.
    et al.
    Samiji, M. E.
    Mbise, G. W.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wennerberg, J.
    Edoff, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Performance comparison of Cu(In,Ga) Se2 solar cells fabricated using RF and DC sputtered ZnO:Al transparent conducting oxides2007Conference paper (Refereed)
  • 75. Olaison, B R
    et al.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Holt, A
    CIGS solar cells with screen-printed contacts2009In: Proceedings of the 24th European Photovoltaic Solar Energy Conference, Hamburg, 2009, p3007, 2009, p. 3007-Conference paper (Refereed)
  • 76. Persson, Clas
    et al.
    Platzer-Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Malmström, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Törndahl, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electronics.
    Strong valence-band offset bowing of ZnO1-xSx enhances p-type nitrogen doping of ZnO-like alloys2006In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 97, no 14, p. 146403-Article in journal (Refereed)
    Abstract [en]

    Photoelectron spectroscopy, optical characterization, and density functional calculations of ZnO1-xSx reveal that the valence-band (VB) offset E-v(x) increases strongly for small S content, whereas the conduction-band edge E-c(x) increases only weakly. This is explained as the formation of local ZnS-like bonds in the ZnO host, which mainly affects the VB edge and thereby narrows the energy gap: E-g(x=0.28)approximate to E-g(ZnO)-0.6 eV. The low-energy absorption tail is a direct Gamma(v)->Gamma(c) transition from ZnS-like VB. The VB bowing can be utilized to enhance p-type N-O doping with lower formation energy Delta H-f and shallower acceptor state in the ZnO-like alloys.

  • 77.
    Pettersson, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Platzer-Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Electrical modeling of Cu(In,Ga)Se2 cells with ALD-Zn1xMgxO bufferlayers2012In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 111, no 1, p. 014509-014509Article in journal (Refereed)
    Abstract [en]

    Electrical modeling of Cu(In,Ga)Se2 solar cells with Zn1-xMgxO buffer layers is performed. A number of  different  device  models  are  implemented  and  tested  by  comparing  simulation  results  and measurement data. Room temperature light-soaking and dark-light cross-over behavior as well aslow-temperature characteristics of these cells are studied. The light-soaking improvements in the solarcell  parameters  are  attributed  to  an  increase  in  buffer  donor  density,  due  to  persistent  photoconductivity, that counteracts charged acceptors in the absorber-buffer region. Dark-light JV-curvecross-over is explained by deep acceptor defects with small electron capture cross-section, in thebuffer. Best correspondence to measurements on ZnO and Zn0.83Mg0.17O cells is obtained with models including absorber-buffer interface acceptor states. No wideband-gap surface defect layer is needed to reproduce measurement data.

  • 78.
    Pettersson, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Platzer-Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Temperature-dependent current-voltage and lightsoaking measurements on Cu(In,Ga)Se2 solar cells with ALD-Zn1-xMgxO buffer layers2009In: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 17, no 7, p. 460-469Article in journal (Refereed)
    Abstract [en]

    In this paper, lightsoaking and temperature-dependent current-voltage (JVT) measurements on Cu(In,Ga)Se2 solar cells with atomic layer deposited Zn1-xMgxO buffer layers are presented. A range of Mg concentrations are used, from pure ZnO (x=0) to 26% Mg (x=0·26). Since this kind of solar cells exhibit strong metastable behaviour, lightsoaking is needed prior to the JVT-measurements to enable fitting of these to the one-diode model. The most prominent effect of lightsoaking cells with Mg-rich buffer layers is an increased fill factor, while the effect on cells with pure ZnO buffer is mainly to increase Voc·. The activation energy is extracted from JVT-measurement data by applying three different methods and the ideality factors are fitted to two different models of temperature-dependence. A buffer layer consisting either of ZnO or Zn1-xMgxO with a minor Mg content gives solar cells dominated by interface recombination, which probably can be related to a negative conduction band offset. A relatively high Mg content in the buffer layer (x=0·21) leads to solar cells dominated by recombination in the space charge region. The recombination is interpreted as being tunnelling-enhanced. The situation in between these Mg concentrations is less clear. Before lightsoaking, the sample with x=0·12 has the highest efficiency of 15·3%, while after lightsoaking the sample with x=0·21 holds the best efficiency, 16·1%, exceeding the value for the CdS reference. The Jsc values of the Zn1-xMgxO cells surpass that of the reference due to the larger bandgap of Zn1-xMgxO compared to CdS.

  • 79.
    Pettersson, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Platzer-Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hultqvist, Adam
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zimmermann, Uwe
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Measurements of photo-induced changes in the conduction properties of ALD-Zn1−xMgxO thin films2010In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T141, p. 014010-1-014010-4Article in journal (Refereed)
    Abstract [en]

    Resistivity and Hall measurements are conducted on atomic layer deposited Zn1−xMgxO thin films of different thicknesses and compositions. It is found that the films exhibit persistent photoconductivity after UV-light exposure. The effect is more pronounced for thinner films with higher magnesium content. These are also the films with the highest resistivity. Light-induced excess conductivity is still present in some of the films after weeks of dark storage. Conductivity relaxation is faster at higher temperatures. From Hall measurements, it is observed that conductivity changes are a combined effect of changes in the mobility and concentration of free carriers.

  • 80.
    Pettersson, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Platzer-Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zimmermann, Uwe
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Baseline model of graded-absorber Cu(In,Ga)Se2 solar cells applied to cells with Zn1−xMgxO buffer layers2011In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 519, no 21, p. 7476-7480Article in journal (Refereed)
    Abstract [en]

    A baseline parameter set for electrical modelling of Cu(In,Ga)Se2 solar cells with compositionally graded absorber and CdS buffer layer is established. The cases with and without Fermi level pinning as well as withand without a surface defect layer are considered. Simulations with a defect layer are observed to give the best correspondence to measurements. Zn1−xMgxO buffer layers are introduced and initial modelling of the lightsoaking behaviour is performed. Simulation results are compared with experimental data.

  • 81.
    Pettersson, Jonas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Törndahl, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Platzer-Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hultqvist, Adam
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    The Influence of Absorber Thickness on Cu(In,Ga)Se-2 Solar Cells With Different Buffer Layers2013In: IEEE Journal of Photovoltaics, ISSN 2156-3381, Vol. 3, no 4, p. 1376-1382Article in journal (Refereed)
    Abstract [en]

    This study investigates the interplay between the absorber layer of Cu(In,Ga)Se-2 solar cells and the other layers of these devices. Cu(In, Ga)Se-2 devices with absorbers of different thicknesses and different buffer layers are fabricated. Absorber layers and finished devices are characterized. Good efficiencies are obtained, also for devices of substandard thickness down to 0.3 mu m. Best open-circuit voltages and fill factors are found for cells with half the standard absorber thickness, but the highest efficiencies are found for cells with the standard thickness of 1.6 mu m due to their higher short-circuit current density. Cu(In, Ga)Se-2 cells with Zn(O,S) buffer layers are more efficient than CdS reference devices for the same absorber thickness due to a higher short-circuit current. For cells with thin absorber layers, a part of the higher current is caused by higher quantum efficiency at long wavelengths. Electrical simulations indicate that the loss in the open-circuit voltage for the thinnest devices is due to recombination in the back contact region. The difference in long-wavelength quantum efficiency between the buffer layers is attributed to a difference in the CIGS band bending. Acceptors at the Cu(In, Ga)Se-2-CdS interface are proposed as an explanation for this difference. A low-quality back contact region enhances the effect.

  • 82.
    Platzer Björkman, Charlotte
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Törndahl, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hultqvist, Adam
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Kessler, John
    Université de Nantes.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Optimization of ALD-(Zn,Mg)O buffer layers and (Zn,Mg)O/Cu(In,Ga)Se-2 interfaces for thin film solar cells2007In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, no 15, p. 6024-6027Article in journal (Refereed)
    Abstract [en]

    (Zn,Mg)O films, fabricated by atomic layer deposition, ALD, are investigated as buffer layers in Cu(In,Ga)Se2-based thin film solar cells. Optimization of the buffer layer is performed in terms of thickness, deposition temperature and composition. High efficiency devices are obtained for deposition at 105–135 °C, whereas losses in open circuit voltage are observed at higher deposition temperatures. The optimal compositional region for (Zn,Mg)O buffer layers in this study is for Mg/(Zn + Mg) contents of about 0.1–0.2, giving band gap values of 3.5–3.7 eV. These devices appear insensitive to thickness variations between 80 and 600 nm. Efficiencies of up to 16.2% are obtained for completely Cd- and S-free devices with (Zn,Mg)O buffer layers deposited with 1000 cycles at 120 °C and having a band gap of 3.6 eV.

  • 83.
    Platzer-Bjorkman, Charlotte
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jani, S.
    Westlinder, J.
    Linnarsson, M. K.
    Scragg, Jonathan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Diffusion of Fe and Na in co-evaporated Cu(In, Ga) Se-2 devices on steel substrates2013In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 535, p. 188-192Article in journal (Refereed)
    Abstract [en]

    In this work we study impurity diffusion into Cu(In, Ga) Se-2 from stainless steel substrates with and without Cr diffusion barriers using secondary ion mass spectrometry. For these substrate configurations we compare cases with and without adding NaF as a sodium precursor. A clear increase in impurity diffusion from the substrate is observed for samples with NaF. Devices made using our micro pilot line show the expected correlation between Fe content, Na content and efficiency, but the highest device efficiency obtained for steel substrates is still slightly below that of the glass substrate reference. We discuss reasons for the observed device performance.

  • 84.
    Platzer-Björkman, Charlotte
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Co-evaporation of CIGS and alternative buffer layers for CIGS devices2011In: Thin film solar cells: Current status and future trends / [ed] Alessio Bosio and Alessandro Romeo, New York: Nova Science Publishers, Inc., 2011, p. 59-90Chapter in book (Other academic)
  • 85.
    Platzer-Björkman, Charlotte
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Scragg, Jonathan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Flammersberger, H
    Kubart, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Influence of precursor sulfur content on film formation and compositional changes in Cu2ZnSnS4 films and solar cells2012In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 98, p. 110-117Article in journal (Refereed)
    Abstract [en]

    Cu2ZnSnS4 (CZTS) thin films are made using sulfurisation of co-sputtered metallic and sulfur-containing precursor films. The CZTS grain size is larger for metallic precursors than for sulfur-containing precursors while more uniform films with fewer voids are obtained in the latter case. During sulfurisation of precursors with tin-excess in closed quartz ampoules, tin is lost from the films with greater losses from metallic precursors. We suggest that the reduced grain size and the reduced tin-loss for sulfur-containing precursors can be explained by a larger number of CZTS nuclei being formed early in the sulfurisation process. In sulfur containing precursors with large tin excess, SnS2 is observed together with CZTS, and a tin-rich bottom layer segregates. This indicates that tin-diffusion in CZTS is relatively slow. Solar cell devices made for a range of compositions at and around stoichiometric CZTS show highest efficiencies in two compositional groups; Zn-rich and Cu-poor/Sn-rich, while close to stoichiometric material gives poor devices. Devices including the tin-rich bottom layer show efficiencies of up to 3.2%. The role of secondary phases such as ZnS and SnS2 on device performance is discussed.

  • 86.
    Platzer-Björkman, Charlotte
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zabierowski, P.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    The role of interfacial elemental selenium in CIGS devices with different buffer layers2008Conference paper (Refereed)
  • 87.
    Platzer-Björkman, Charlotte
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zabierowski, P.
    Pettersson, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Törndahl, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Improved fill factor and open circuit voltage by crystalline selenium at the Cu(In,Ga)Se-2/buffer layer interface in thin film solar cells2010In: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 18, no 4, p. 249-256Article in journal (Refereed)
    Abstract [en]

    A surface treatment by evaporated selenium on Cu(In,Ga)Se, (CIGS) is shown to improve open circuit voltage, V and in some cases fill factor, FF, in solar cells with CdS, (Zn,Mg)O or Zn(O,S) buffer layers. V increases with increasing amount of crystalline Se, while FF improves only for small amounts. The improvements are counteracted by a decreasing short circuit current assigned to absorption in hexagonal Se. Improved efficiency is shown for device structures with (Zn,Mg)0 and Zn(O,S) buffer layers by atomic layer deposition. Analysis by grazing incidence X-ray diffraction and photoelectron spectroscopy show partial coverage of the CIGS surface by hexagonal selenium. The effects on device performance from replacing part of the CIGS/buffer interface area by a Se/buffer junction are discussed.

  • 88. Powalla, Michael
    et al.
    Kessler, Friedrich
    Hariskos, Dimitrios
    Voorwinden, Georg
    Tiwari, Ayodhya N
    Brémaud, David
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Schleussner, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Stolt, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Dimmler, Bernhard
    Wächter, Rolf
    Klenk, Reiner
    Pistor, Paul
    Abou-Ras, Daniel
    Schock, Hans-Werner
    Kerrec, Olivier
    Grand, Pierre-Philippe
    Lincot, Daniel
    Naghavi, Negar
    Pérez-Rodrigues, Alejandro
    Auvray, Stéphane
    Highly productive manufacturing of CIS-based large-area modules2007Conference paper (Refereed)
  • 89. Przado, D.
    et al.
    Igalson, M.
    Bacewicz, R.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    The influence of metastabilities on the luminescence in the Cu(In,Ga)Se2 solar cells2007In: Acta Physica Polonica. A, ISSN 0587-4246, E-ISSN 1898-794X, Vol. 112, no 2, p. 183-189Article in journal (Refereed)
    Abstract [en]

    Photoluminescence and electroluminescence spectra of the absorber layer in ZnO/CdS/Cu(In,Ga)Se-2 solar cells were measured. Their dependence on temperature, excitation intensity and applied voltage were studied. Electroluminescence measurements were used to investigate light- and bias-induced metastabilities in the absorber of the cells. We showed that metastable changes of defect distributions, which produce an effect on the electrical characteristics of ZnO/CdS/Cu(In,Ga)Se2 material, affect also the luminescence yield. The dependence of the intensity and shape of the electroluminescence spectra on the state of the sample is observed. These results fit well into the theoretical calculations of Lany and Zunger model showing that divacancy complex (V-Sc-V-Cu) is responsible for metastable changes observed in ZnO/CdS/Cu (In, Ga) Se-2-based solar cells. We conclude that during light soaking or/and forward bias the probability of nonradiative recombination is decreased.

  • 90.
    Ren, Yi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Scragg, Jonathan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Larsen, Jes
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Platzer-Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Evolution of Na-S(-O) compounds on the Cu2ZnSnS4 absorber surface and their effects on CdS thin film growth2016In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, no 28, p. 18600-18607Article in journal (Refereed)
    Abstract [en]

    Formation of Na-containing surface compounds is an important phenomenon in the Cu2ZnSnS4 (CZTS) quaternary material synthesis for solar cell applications. Still, identification of these compounds and the understanding of their potential influence on buffer layer growth and device performance are scarce. In this work, we discovered that the evolution of Na-S(-O) compounds on the CZTS surface substantially affect the solution/CZTS interface during the chemical bath deposition of CdS buffer film. We showed that Na2S negatively affects the growth of CdS, and that this compound is likely to form on the CZTS surface after annealing. It was also demonstrated that the Na2S compound can be oxidized to Na2SO4 by air exposure of the annealed CZTS surface or be removed using water dipping instead of the commonly used KCN etching process, resulting in significantly better quality of the CdS layer. Lastly, 6.5% CZTS solar cells were fabricated with air exposure treatment without incorporation of the KCN etching process. This work provides new insight into the growth of the CdS/CZTS interface for solar cell applications and opens new possibilities for improving likewise Cd-free buffer materials that are grown with a similar chemical bath deposition process.

  • 91.
    Ren, Yi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Scragg, Jonathan J.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Platzer Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Evolution of Na-S(-O) compounds on Cu2ZnSnS4 absorber surface and its effect on CdS growth2016In: 2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC), New York: IEEE, 2016, p. 2255-2257Conference paper (Refereed)
    Abstract [en]

    Na-containing surface compounds is likely to form during the formation of CZTS absorber. Still, the understanding of any potential influence on buffer layer growth and device performance is limited. In this work, we observed that NaxS compound can possibly form on the CZTS surface after annealing, and negatively affect the growth of the subsequent CdS buffer. The NaxS compound is oxidized to Na2SO4 via air exposing the annealed CZTS surface, which allows greatly improved quality of the CdS layer. This provides new insights for improving the CdS/CZTS interface during the fabrication of CZTS solar cells.

  • 92.
    Retterstol Olaisen, Birger
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Woldegiorgis, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Westin, Per-Oskar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Stolt, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    CIGS Mini-Modules with Screen-Printed Front Contacts2005In: Technical Digest of the 15th International Photovoltaic Science and Engineering Conference, Shanghai, China, 2005Conference paper (Refereed)
  • 93.
    Salome, P. M. P.
    et al.
    Int Iberian Nanotechnol Lab, P-4715330 Braga, Portugal..
    Keller, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Törndahl, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Teixeira, J. P.
    Univ Aveiro, Dept Fis & I3N, P-3810193 Aveiro, Portugal..
    Nicoara, N.
    Int Iberian Nanotechnol Lab, P-4715330 Braga, Portugal..
    Andrade, R. -Ribeiro
    Int Iberian Nanotechnol Lab, P-4715330 Braga, Portugal.;Univ Fed Minas Gerais, Dept Fis, Inst Ciencias Exatas, Caixa Postal 702, BR-30123970 Belo Horizonte, MG, Brazil..
    Stroppa, D. G.
    Int Iberian Nanotechnol Lab, P-4715330 Braga, Portugal..
    Gonzalez, J. C.
    Univ Fed Minas Gerais, Dept Fis, Inst Ciencias Exatas, Caixa Postal 702, BR-30123970 Belo Horizonte, MG, Brazil..
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Leitao, J. P.
    Univ Aveiro, Dept Fis & I3N, P-3810193 Aveiro, Portugal..
    Sadewasser, S.
    Int Iberian Nanotechnol Lab, P-4715330 Braga, Portugal..
    CdS and Zn1-xSnxOy buffer layers for CIGS solar cells2017In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 159, p. 272-281Article in journal (Refereed)
    Abstract [en]

    Thin film solar cells based on Cu(In,Ga)Se-2 (CIGS), where just the buffer layer is changed, were fabricated and studied. The effects of two different buffer layers, CdS and Zn1-xSnxOy (ZnSnO), are compared using several characterization techniques. We compared both devices and observe that the ZnSnO-based solar cells have similar values of power conversion efficiency as compared to the cells with CdS buffer layers. The ZnSnO-based devices have higher values in the short-circuit current (6) that compensate for lower values in fill factor (FF) and open circuit voltage (V-oc) than CdS based devices. Kelvin probe force microscopy (KPFM) results indicate that CdS provides junctions with slightly higher surface photovoltage (SPV) than ZnSnO, thus explaining the lower Voc potential for the ZnSnO sample. The TEM analysis shows a poly-crystalline ZnSnO layer and we have not detected any strong evidence of diffusion of Zn or Sn into the CIGS. From the photoluminescence measurements, we concluded that both samples are being affected by fluctuating potentials, although this effect is higher for the CdS sample.

  • 94.
    Salome, Pedro M. P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Fjällström, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Szaniawski, Piotr
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Leitao, Joaquim P.
    Hultqvist, Adam
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Fernandes, Paulo A.
    Teixeira, Jennifer P.
    Falcao, Bruno P.
    Zimmermann, Uwe
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    da Cunha, Antonio F.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    A comparison between thin film solar cells made from co-evaporated CuIn1-xGaxSe2 using a one-stage process versus a three-stage process2015In: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 23, no 4, p. 470-478Article in journal (Refereed)
    Abstract [en]

    Until this day, the most efficient Cu(In,Ga)Se-2 thin film solar cells have been prepared using a rather complex growth process often referred to as three-stage or multistage. This family of processes is mainly characterized by a first step deposited with only In, Ga and Se flux to form a first layer. Cu is added in a second step until the film becomes slightly Cu-rich, where-after the film is converted to its final Cu-poor composition by a third stage, again with no or very little addition of Cu. In this paper, a comparison between solar cells prepared with the three-stage process and a one-stage/in-line process with the same composition, thickness, and solar cell stack is made. The one-stage process is easier to be used in an industrial scale and do not have Cu-rich transitions. The samples were analyzed using glow discharge optical emission spectroscopy, scanning electron microscopy, X-ray diffraction, current-voltage-temperature, capacitance-voltage, external quantum efficiency, transmission/reflection, and photoluminescence. It was concluded that in spite of differences in the texturing, morphology and Ga gradient, the electrical performance of the two types of samples is quite similar as demonstrated by the similar J-V behavior, quantum spectral response, and the estimated recombination losses. 

  • 95.
    Salome, Pedro M. P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hultqvist, Adam
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Fjällström, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Aitken, B. G.
    Zhang, K.
    Fuller, K.
    Williams, C. Kosik
    Incorporation of Na in Cu(In,Ga)Se-2 Thin-Film Solar Cells: A Statistical Comparison Between Na From Soda-Lime Glass and From a Precursor Layer of NaF2014In: IEEE Journal of Photovoltaics, ISSN 2156-3381, E-ISSN 2156-3403, Vol. 4, no 6, p. 1659-1664Article in journal (Refereed)
    Abstract [en]

    The presence of Na in Cu(In,Ga)Se-2 layers increases the electrical performance of this type of thin- film solar cell. A detailed comparison of incorporating Na in the CIGS layer by two different methods is performed by evaluating several hundred devices fabricated under similar conditions. The firstmethod is based on the conventionally used Na diffusion from the soda-lime glass substrate, whereas the second method is based on a NaF precursor layer deposited on a Mo- coated alkali- free glass substrate. The sample where Na is introduced by using a NaF precursor layer shows an orientation weighted toward (2 0 4)/(2 2 0) and a net acceptor concentration of 3.4 x 10(16) cm(-3), while SLG shows a (1 1 2) orientation with a 2.9 x 10(16) cm(-3) acceptor concentration. Both sample types show close identical elemental depth profiles, morphology, and electrical performance.

  • 96.
    Salome, Pedro M. P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hultqvist, Adam
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Fjällström, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Vermang, Bart
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Aitken, B.
    Zhang, K.
    Fuller, K.
    Williams, C. Kosik
    The effect of high growth temperature on Cu(In,Ga)Se-2 thin film solar cells2014In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 123, p. 166-170Article in journal (Refereed)
    Abstract [en]

    The morphological, elemental distribution and electrical performance effects of increasing the Cu(In,Ga) Se-2 (CIGS) growth substrate temperature are studied. While the increased substrate growth temperature with no other modifications led to increased CIGS grain size, it also resulted in depth profile flattening of the [Ga]/([Ga]+[In]) ratio. Tuning the Ga profile in the high temperature process led to a more desirable [Ga]/([Ga]+[In]) depth profile and allowed a comparison between high and standard temperature. Devices prepared at higher temperature showed an improved grain size and the electrical performance is very similar to that of the reference sample prepared at a standard temperature.

  • 97.
    Salome, Pedro M. P.
    et al.
    Int Iberian Nanotechnol Lab, P-4715330 Braga, Portugal..
    Ribeiro-Andrade, Rodrigo
    Int Iberian Nanotechnol Lab, P-4715330 Braga, Portugal.;Univ Fed Minas Gerais, Dept Fis, BR-30123970 Belo Horizonte, MG, Brazil..
    Teixeira, Jennifer P.
    Univ Aveiro, Dept Fis, P-3810193 Aveiro, Portugal.;Univ Aveiro, I3N, P-3810193 Aveiro, Portugal..
    Keller, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Törndahl, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Nicoara, Nicoleta
    Int Iberian Nanotechnol Lab, P-4715330 Braga, Portugal..
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Gonzalez, Juan Carlos
    Univ Fed Minas Gerais, Dept Fis, BR-30123970 Belo Horizonte, MG, Brazil..
    Leitao, Joaquim Pratas
    Univ Aveiro, Dept Fis, P-3810193 Aveiro, Portugal.;Univ Aveiro, I3N, P-3810193 Aveiro, Portugal..
    Sadewasser, Sascha
    Int Iberian Nanotechnol Lab, P-4715330 Braga, Portugal..
    Cd and Cu Interdiffusion in Cu(In, Ga) Se-2/CdS Hetero-Interfaces2017In: IEEE Journal of Photovoltaics, ISSN 2156-3381, E-ISSN 2156-3403, Vol. 7, no 3, p. 858-863Article in journal (Refereed)
    Abstract [en]

    We report a detailed characterization of an industrylike prepared Cu(In, Ga) Se-2 (CIGS)/CdS heterojunction by scanning transmission electron microscopy and photoluminescence (PL). Energy dispersive X-ray spectroscopy shows the presence of several regions in the CIGS layer that are Cu deprived and Cd enriched, suggesting the segregation of Cd-Se. Concurrently, the CdS layer shows Cd-deprived regions with the presence of Cu, suggesting a segregation of Cu-S. The two types of segregations are always found together, which, to the best of our knowledge, is observed for the first time. The results indicate that there is a diffusion process that replaces Cu with Cd in the CIGS layer and Cd with Cu in the CdS layer. Using a combinatorial approach, we identified that this effect is independent of focused-ion beam sample preparation and of the transmission electron microscopy grid. Furthermore, PL measurements before and after an HCl etch indicate a lower degree of defects in the postetch sample, compatible with the segregates removal. We hypothesize that Cu2-x Se nanodomains react during the chemical bath process to form these segregates since the chemical reaction that dominates this process is thermodynamically favorable. These results provide important additional information about the formation of the CIGS/CdS interface.

  • 98.
    Salome, Pedro M. P.
    et al.
    Int Iberian Nanotechnol Lab, P-4715330 Braga, Portugal.;Univ Aveiro, Dept Fis, P-3810193 Aveiro, Portugal..
    Vermang, Bart
    Univ Hasselt Partner Solliance, Agoralaan Gebouw H, B-3590 Diepenbeek, Belgium.;Imec Partner Solliance, Kapeldreef 75, B-3001 Leuven, Belgium.;Imomec Partner Solliance, Wetenschapspk 1, B-3590 Diepenbeek, Belgium..
    Ribeiro-Andrade, Rodrigo
    Int Iberian Nanotechnol Lab, P-4715330 Braga, Portugal.;Univ Fed Minas Gerais, Dept Fis, BR-30123970 Belo Horizonte, MG, Brazil..
    Teixeira, Jennifer P.
    Univ Aveiro, Dept Fis, P-3810193 Aveiro, Portugal..
    Cunha, Jose M. V.
    Int Iberian Nanotechnol Lab, P-4715330 Braga, Portugal.;Univ Nova Lisboa, Fac Sci & Technol, Dept Mat Sci, CENIMAT i3N, P-2829516 Caparica, Portugal.;CEMOP UNINOVA, Campus Caparica, P-2829516 Caparica, Portugal..
    Mendes, Manuel J.
    Univ Nova Lisboa, Fac Sci & Technol, Dept Mat Sci, CENIMAT i3N, P-2829516 Caparica, Portugal.;CEMOP UNINOVA, Campus Caparica, P-2829516 Caparica, Portugal..
    Haque, Sirazul
    Univ Nova Lisboa, Fac Sci & Technol, Dept Mat Sci, CENIMAT i3N, P-2829516 Caparica, Portugal.;CEMOP UNINOVA, Campus Caparica, P-2829516 Caparica, Portugal..
    Borme, Jerome
    Int Iberian Nanotechnol Lab, P-4715330 Braga, Portugal..
    Aguas, Hugo
    Univ Nova Lisboa, Fac Sci & Technol, Dept Mat Sci, CENIMAT i3N, P-2829516 Caparica, Portugal.;CEMOP UNINOVA, Campus Caparica, P-2829516 Caparica, Portugal..
    Fortunato, Elvira
    Univ Nova Lisboa, Fac Sci & Technol, Dept Mat Sci, CENIMAT i3N, P-2829516 Caparica, Portugal.;CEMOP UNINOVA, Campus Caparica, P-2829516 Caparica, Portugal..
    Martins, Rodrigo
    Univ Nova Lisboa, Fac Sci & Technol, Dept Mat Sci, CENIMAT i3N, P-2829516 Caparica, Portugal.;CEMOP UNINOVA, Campus Caparica, P-2829516 Caparica, Portugal..
    Gonzalez, Juan C.
    Univ Fed Minas Gerais, Dept Fis, BR-30123970 Belo Horizonte, MG, Brazil..
    Leitao, Joaquim P.
    Univ Aveiro, Dept Fis, P-3810193 Aveiro, Portugal..
    Fernandes, Paulo A.
    Int Iberian Nanotechnol Lab, P-4715330 Braga, Portugal.;Univ Aveiro, Dept Fis, P-3810193 Aveiro, Portugal.;Inst Politecn Porto, Inst Super Engn Porto, Dept Fis, CIETI, Rua Dr Antonio Bernardino Almeida 431, P-4200072 Oporto, Portugal..
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Sadewasser, Sascha
    Int Iberian Nanotechnol Lab, P-4715330 Braga, Portugal..
    Passivation of Interfaces in Thin Film Solar Cells: Understanding the Effects of a Nanostructured Rear Point Contact Layer2018In: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 5, no 2, article id 1701101Article in journal (Refereed)
    Abstract [en]

    Thin film solar cells based in Cu(In,Ga)Se-2 (CIGS) are among the most efficient polycrystalline solar cells, surpassing CdTe and even polycrystalline silicon solar cells. For further developments, the CIGS technology has to start incorporating different solar cell architectures and strategies that allow for very low interface recombination. In this work, ultrathin 350 nm CIGS solar cells with a rear interface passivation strategy are studied and characterized. The rear passivation is achieved using an Al2O3 nanopatterned point structure. Using the cell results, photoluminescence measurements, and detailed optical simulations based on the experimental results, it is shown that by including the nanopatterned point contact structure, the interface defect concentration lowers, which ultimately leads to an increase of solar cell electrical performance mostly by increase of the open circuit voltage. Gains to the short circuit current are distributed between an increased rear optical reflection and also due to electrical effects. The approach of mixing several techniques allows us to make a discussion considering the different passivation gains, which has not been done in detail in previous works. A solar cell with a nanopatterned rear contact and a 350 nm thick CIGS absorber provides an average power conversion efficiency close to 10%.

    The full text will be freely available from 2018-12-05 00:00
  • 99.
    Salomé, Pedro
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Fjällström, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hultqvist, Adam
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Na doping of CIGS solar cells using low sodium-doped mo layer2013In: IEEE Journal of Photovoltaics, ISSN 2156-3381, Vol. 3, no 1, p. 509-513Article in journal (Refereed)
    Abstract [en]

    Na plays an important role in the electrical performance of Cu(In,Ga)Se2 (CIGS) thin-film solar cells. Traditionally, Na has been introduced during the growth of CIGS by thermal diffusion from the soda-lime glass (SLG) substrate; however, better control of the amount of Na is needed to have a more precise control of growth conditions. The introduction of Na into CIGS was studied in three different ways: from the SLG, from a NaF precursor, and from a Na-doped Mo (MoNa) back contact. The most successful approaches were obtained by using the conventional SLG and the NaF precursor. Different growth temperatures of CIGS were tested in an attempt to diffuse more Na from the MoNa layer.

  • 100.
    Salomé, Pedro M. P.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Fjällström, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hultqvist, Adam
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Szaniawski, Piotr
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zimmermann, Uwe
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Edoff, Marika
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    The effect of Mo back contact ageing on Cu(In,Ga)Se-2 thin-film solar cells2014In: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 22, no 1, p. 83-89Article in journal (Refereed)
    Abstract [en]

    In this work, we investigate the effect of ageing Mo-coated substrates in a dry and N-2 flooded cabinet. The influence was studied by preparing Cu(In,Ga)Se-2 solar cells and by comparing the electrical performance with devices where the Mo layer was not aged. The measurements used for this study were current-voltage (J-V), external quantum efficiency (EQE), secondary ion mass spectroscopy (SIMS) and capacitance-voltage (C-V). It was concluded that devices prepared with the aged Mo layer have, in average, an increase of 0.8% in efficiency compared with devices that had a fresh Mo layer. Devices with aged Mo exhibited a nominal increase of 12.5mV of open circuit voltage, a decrease of 1.1mA/cm(-2) of short circuit current and a fill factor increase of 2.4%. Heat treatment of fresh Mo layers in oxygen atmosphere was also studied as an alternative to ageing and was shown to provide a similar effect to the aged device's performance. 

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