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Publications (10 of 149) Show all publications
Donzel-Gargand, O., Thersleff, T., Keller, J., Törndahl, T., Larsson, F., Wallin, E., . . . Edoff, M. (2018). Deep surface Cu depletion induced by K in high-efficiency Cu(In,Ga)Se2 solar cell absorbers. Progress in Photovoltaics
Open this publication in new window or tab >>Deep surface Cu depletion induced by K in high-efficiency Cu(In,Ga)Se2 solar cell absorbers
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2018 (English)In: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159XArticle in journal (Refereed) Epub ahead of print
Abstract [en]

In this work, we used K‐rich glass substrates to provide potassium during the coevaporation of Cu(In,Ga)Se2 (CIGS) absorber layers. Subsequently, we applied a postdeposition treatment (PDT) using KF or RbF to some of the grown absorbers. It was found that the presence of K during the growth of the CIGS layer led to cell effi- ciencies beyond 17%, and the addition of a PDT pushed it beyond 18%. The major finding of this work is the observation of discontinuous 100‐ to 200‐nm‐deep Cu‐ depleted patches in the vicinity of the CdS buffer layer, correlated with the presence of K during the growth of the absorber layer. The PDT had no influence on the forma- tion of these patches. A second finding concerns the composition of the Cu‐depleted areas, where an anticorrelation between Cu and both In and K was measured using scanning transmission electron microscopy. Furthermore, a steeper Ga/(In+Ga) ratio gradient was measured for the absorbers grown with the presence of K, suggesting that K hinders the group III element interdiffusion. Finally, no Cd in‐diffusion to the CIGS layer could be detected. This indicates that if CdCu substitution occurs, either their concentration is below our instrumental detection limit or its presence is contained within the first 6 nm from the CdS/CIGS interface.

Keywords
CIGS, Cu depletion, EELS, OVC, Raman, solar cell, TEM
National Category
Other Materials Engineering Energy Systems
Identifiers
urn:nbn:se:uu:diva-357120 (URN)10.1002/pip.3010 (DOI)
Available from: 2018-08-12 Created: 2018-08-12 Last updated: 2018-08-15Bibliographically approved
Ledinek, D., Donzel-Gargand, O., Sköld, M., Keller, J. & Edoff, M. (2018). Effect of different Na supply methods on thin Cu(In,Ga)Se2 solar cells with Al2O3 rear passivation layers. Solar Energy Materials and Solar Cells
Open this publication in new window or tab >>Effect of different Na supply methods on thin Cu(In,Ga)Se2 solar cells with Al2O3 rear passivation layers
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2018 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398Article in journal (Refereed) Published
Abstract [en]

In this work, rear-contact passivated Cu(In,Ga)Se2 (CIGS) solar cells were fabricated without any intentional contact openings between the CIGS and Mo layers. The investigated samples were either Na free or one of two Na supply methods was used, i) a NaF precursor on top of the Al2O3 rear passivation layer or ii) an in situ post- deposition treatment with NaF after co-evaporation of the CIGS layer. The thickness of the ALD-Al2O3 passi- vation layer was also varied in order to find an optimal combination of Na supply and passivation layer thickness. Our results from electrical characterization show remarkably different solar cell behavior for different Na supplies. For up to 1nm thick Al2O3 layers an electronically good contact could be confirmed independently of Na deposition method and content. When the Al2O3 thickness exceeded 1 nm, the current was blocked on all samples except on the samples with the NaF precursor. On these samples the current was not blocked up to an Al2O3 layer thickness of about 6 nm, the maximum thickness we could achieve without the CIGS peeling off the Al2O3 layer. Transmission electron microscopy reveals a porous passivation layer for the samples with a NaF precursor. An analysis of the dependence of the open circuit voltage on temperature (JVT) indicates that a thicker NaF precursor layer lowers the height of the hole barrier at the rear contact for the passivated cells. This energy barrier is also lower for the passivated sample, compared to an unpassivated sample, when both samples have been post-deposition treated.

Keywords
Alkali Back contact CIGS Passivation Thin films Rear contact Tunneling
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Energy Systems Other Materials Engineering
Identifiers
urn:nbn:se:uu:diva-357123 (URN)10.1016/j.solmat.2018.07.017 (DOI)
Available from: 2018-08-12 Created: 2018-08-12 Last updated: 2018-08-12
Keller, J., Chalvet, F., Joel, J., Aijaz, A., Kubart, T., Riekehr, L., . . . Törndahl, T. (2018). Effect of KF absorber treatment on the functionality of different transparent conductive oxide layers in CIGSe solar cells. Progress in Photovoltaics, 26(1), 13-23
Open this publication in new window or tab >>Effect of KF absorber treatment on the functionality of different transparent conductive oxide layers in CIGSe solar cells
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2018 (English)In: Progress in Photovoltaics, ISSN 1062-7995, E-ISSN 1099-159X, Vol. 26, no 1, p. 13-23Article in journal (Refereed) Published
Abstract [en]

This contribution studies the impact of the KF-induced Cu(In,Ga)Se2 (CIGSe) absorber modification on the suitability of different transparent conductive oxide (TCO) layers in solar cells. The TCO material was varied between ZnO:Al (AZO), ZnO:B (BZO), and In2O3:H (IOH). It is shown that the thermal stress needed for optimized TCO properties can establish a transport barrier for charge carriers, which results in severe losses in fill factor (FF) for temperatures >150°C. The FF losses are accompanied by a reduction in open circuit voltage (Voc) that might originate from a decreased apparent doping density (Nd,app) after annealing. Thermally activated redistributions of K and Na in the vicinity of the CdS/(Cu,K)-In-Se interface are suggested to be the reason for the observed degradation in solar cell performance. The highest efficiency was measured for a solar cell where the absorber surface modification was removed and a BZO TCO layer was deposited at a temperature of 165°C. The presented results highlight the importance of well-designed TCO and buffer layer processes for CIGSe solar cells when a KF post deposition treatment (KF-PDT) was applied.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-332827 (URN)10.1002/pip.2925 (DOI)000418097200002 ()
Funder
Swedish Energy Agency, 2012-004591
Available from: 2017-11-02 Created: 2017-11-02 Last updated: 2018-01-17Bibliographically approved
Salome, P. M. P., Vermang, B., Ribeiro-Andrade, R., Teixeira, J. P., Cunha, J. M. V., Mendes, M. J., . . . Sadewasser, S. (2018). Passivation of Interfaces in Thin Film Solar Cells: Understanding the Effects of a Nanostructured Rear Point Contact Layer. Advanced Materials Interfaces, 5(2), Article ID 1701101.
Open this publication in new window or tab >>Passivation of Interfaces in Thin Film Solar Cells: Understanding the Effects of a Nanostructured Rear Point Contact Layer
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2018 (English)In: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 5, no 2, article id 1701101Article in journal (Refereed) Published
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%.

Keywords
Cu(In, Ga)Se-2 (CIGS), nanofabrication, passivation, photovoltaics, semiconductors, thin film solar cells
National Category
Physical Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-343670 (URN)10.1002/admi.201701101 (DOI)000423173800013 ()
Funder
EU, Horizon 2020, 720887EU, European Research Council, 715027
Available from: 2018-03-07 Created: 2018-03-07 Last updated: 2018-07-05Bibliographically approved
Ledinek, D., Salome, P., Hägglund, C., Zimmermann, U. & Edoff, M. (2018). Rear Contact Passivation for High Bandgap Cu(In, Ga)Se2 Solar Cells With a Flat Ga profile. IEEE Journal of Photovoltaics, 8(3), 864-870
Open this publication in new window or tab >>Rear Contact Passivation for High Bandgap Cu(In, Ga)Se2 Solar Cells With a Flat Ga profile
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2018 (English)In: IEEE Journal of Photovoltaics, ISSN 2156-3381, E-ISSN 2156-3403, Vol. 8, no 3, p. 864-870Article in journal (Refereed) Published
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.

Keywords
Back contact, CIGS, CIGSe, Cu(In, Ga)Se-2, energy barrier, passivation, rear contact, thin films, two-diode model
National Category
Condensed Matter Physics Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-356073 (URN)10.1109/JPHOTOV.2018.2813259 (DOI)000430718700029 ()
Funder
Swedish Energy AgencyStandUp
Available from: 2018-07-13 Created: 2018-07-13 Last updated: 2018-07-25Bibliographically approved
Szaniawski, P., Olsson, J., Frisk, C., Fjällström, V., Ledinek, D., Larsson, F., . . . Edoff, M. (2017). A Systematic Study of Light-On-Bias Behavior in Cu(In,Ga)Se2 Solar Cells With Varying Absorber Compositions. IEEE Journal of Photovoltaics, 7(3), 882-891
Open this publication in new window or tab >>A Systematic Study of Light-On-Bias Behavior in Cu(In,Ga)Se2 Solar Cells With Varying Absorber Compositions
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2017 (English)In: IEEE Journal of Photovoltaics, ISSN 2156-3381, E-ISSN 2156-3403, Vol. 7, no 3, p. 882-891Article in journal (Refereed) Published
Abstract [en]

Light-on-bias effects were investigated in multiple Cu(In, Ga)Se2 solar cells with varying absorber layer compositions. A strong link between deformations caused by red-on-bias treatments in current-voltage (IV ) and capacitance-voltage (CV) characteristics was demonstrated. Similarly to red-on-bias, blue-on-bias leads to a local increase in static negative charge, but in samples with CdS buffers this increase is shifted away from the interface and has no impact on device performance. IV characteristics of samples with Cd-free buffers are not affected by any light-on-bias treatments, suggesting that CdS plays a vital role in the decreased performance after red-on-bias. A statistical approach was used to search for compositional trends in red-on-bias behavior. Deformation factors were defined for IV and CV characteristics before and after the treatment. While there is a strong relationship between the deformations observed in both types of measurements, the degree to which red-on-bias affects IV and CV curves can vary dramatically. These variations cannot be attributed to changes in composition, since no clear compositional trends were found. Rather, other factors related to sample manufacturing and to the buffer layer seem to have major impact on red-on-bias behavior.

Keywords
Capacitance;Charge measurement;Current measurement;Light emitting diodes;Lighting;Photovoltaic cells;Temperature measurement;Capacitance-voltage characteristics;current-voltage characteristics;degradation;deposition and characterization of thin film PV absorbers;photovoltaic cells;photovoltaic effects;thin film PV device properties and modeling
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-319426 (URN)10.1109/JPHOTOV.2017.2655148 (DOI)000399992000023 ()
Available from: 2017-04-04 Created: 2017-04-04 Last updated: 2018-07-13Bibliographically approved
Szaniawski, P., Zabierowski, P., Olsson, J., Zimmermann, U. & Edoff, M. (2017). Advancing the understanding of reverse breakdown in Cu(In,Ga)Se2 solar cells. IEEE Journal of Photovoltaics, 7(4), 1136-1142
Open this publication in new window or tab >>Advancing the understanding of reverse breakdown in Cu(In,Ga)Se2 solar cells
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2017 (English)In: IEEE Journal of Photovoltaics, ISSN 2156-3381, E-ISSN 2156-3403, Vol. 7, no 4, p. 1136-1142Article in journal (Refereed) Published
Abstract [en]

Reverse breakdown is investigated in multiple Cu(In,Ga)Se-2 solar cells with varying buffer layer thicknesses. A method to extract transition voltage, which marks the change of conduction mechanism that leads to electrical breakdown, is described as an alternative to the often less-meaningful breakdown voltage. Transition voltages for samples with CdS and ZnxSn1-xOy buffers are extracted from breakdown measurements performed in darkness and under illumination. The electric field is calculated for ZTO-based samples measured in darkness, and its implications for the energy band structure are examined. Fowler-Nordheim tunneling and Poole-Frenkel conduction are considered as candidates for the main breakdown mechanism in darkness. A model combining the two conduction mechanisms is proposed, and fits for experimental data are presented and discussed. Involvement of defects is debated, and defect-andbreakdown- related phenomena are showcased.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-319442 (URN)10.1109/JPHOTOV.2017.2699860 (DOI)000404258900027 ()
Available from: 2017-04-04 Created: 2017-04-04 Last updated: 2017-09-12Bibliographically approved
Zhang, J., Hultqvist, A., Zhang, T., Jiang, L., Ruan, C., Yang, L., . . . Johansson, E. (2017). Al2O3 Underlayer Prepared by Atomic Layer Deposition for Efficient Perovskite Solar Cells.. ChemSusChem, 10(19), 3810-3817
Open this publication in new window or tab >>Al2O3 Underlayer Prepared by Atomic Layer Deposition for Efficient Perovskite Solar Cells.
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2017 (English)In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 10, no 19, p. 3810-3817Article in journal (Refereed) Published
Abstract [en]

Perovskite solar cells, as an emergent technology for solar energy conversion, have attracted much attention in the solar cell community by demonstrating impressive enhancement in power conversion efficiencies. However, the high temperature and manually processed TiO2 underlayer prepared by spray pyrolysis significantly limit the large-scale application and device reproducibility of perovskite solar cells. In this study, lowtemperature atomic layer deposition (ALD) is used to prepare a compact Al2 O3 underlayer for perovskite solar cells. The thickness of the Al2 O3 layer can be controlled well by adjusting the deposition cycles during the ALD process. An optimal Al2 O3 layer effectively blocks electron recombination at the perovskite/fluorine-doped tin oxide interface and sufficiently transports electrons through tunneling. Perovskite solar cells fabricated with an Al2 O3 layer demonstrated a highest efficiency of 16.2 % for the sample with 50 ALD cycles (ca. 5 nm), which is a significant improvement over underlayer-free PSCs, which have a maximum efficiency of 11.0 %. Detailed characterization confirms that the thickness of the Al2 O3 underlayer significantly influences the charge transfer resistance and electron recombination processes in the devices. Furthermore, this work shows the feasibility of using a high band-gap semiconductor such as Al2 O3 as the underlayer in perovskite solar cells and opens up pathways to use ALD Al2 O3 underlayers for flexible solar cells.

Keywords
atomic layer deposition, electron transport, perovskites, semiconductors, solar cells
National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-336200 (URN)10.1002/cssc.201701160 (DOI)000428425000017 ()28857493 (PubMedID)
Funder
Swedish Energy AgencyÅForsk (Ångpanneföreningen's Foundation for Research and Development)Swedish Research CouncilSwedish Research Council FormasKnut and Alice Wallenberg Foundation
Available from: 2017-12-12 Created: 2017-12-12 Last updated: 2018-07-18Bibliographically approved
Bilousov, O. V., Ren, Y., Törndahl, T., Donzel-Gargand, O., Ericson, T., Platzer Björkman, C., . . . Hägglund, C. (2017). ALD of phase controlled tin monosulfide thin films. In: : . Paper presented at Joint EuroCVD 21 – Baltic ALD 15.
Open this publication in new window or tab >>ALD of phase controlled tin monosulfide thin films
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2017 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

Tin monosulfide (SnS) is a promising semiconductor material for low-cost conversion of solar energy, playing the role of absorber layer in photovoltaic devices. SnS is, due to its high optical damping, also an excellent semiconductor candidate for the realization of ultrathin (nanoscale thickness) plasmonic solar cells [1].

Here, we present an important step to further control and understand SnS film properties produced using low temperature ALD with Sn(acac)2 and H2S as precursors. We show that the SnS film properties vary over a rather wide range depending on substrate temperature and reaction conditions, and that this is connected to the growth of cubic (π-SnS) and orthorhombic SnS phases. The optical properties of the two polymorphs differ significantly, as demonstrated by spectroscopic ellipsometry [2].

1. C. Hägglund, G. Zeltzer, R. Ruiz, A. Wangperawong, K. E. Roelofs, S. F. Bent, ACS Photonics 3 (3) (2016) 456–463.

2. O. V. Bilousov, Y. Ren, T. Törndahl, O. Donzel-Gargand , T. Ericson, C. Platzer-Björkman, M. Edoff, and C. Hägglund, ACS Chemistry of Materials  29 (7) (2017) 2969–2978.

Keywords
atomic layer deposition, thin films, solar cells, semiconductors
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-335501 (URN)
Conference
Joint EuroCVD 21 – Baltic ALD 15
Projects
Ultrathin nanocomposite absorbers and heterojunctions for solar cells
Funder
Swedish Research Council, 621-2014-5599
Available from: 2017-12-06 Created: 2017-12-06 Last updated: 2017-12-29Bibliographically approved
Bilousov, O. V., Ren, Y., Törndahl, T., Donzel-Gargand, O., Ericson, T., Platzer-Björkman, C., . . . Hägglund, C. (2017). Atomic Layer Deposition of Cubic and Orthorhombic Phase Tin Monosulfide. Chemistry of Materials, 29(7), 2969-2978
Open this publication in new window or tab >>Atomic Layer Deposition of Cubic and Orthorhombic Phase Tin Monosulfide
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2017 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, no 7, p. 2969-2978Article in journal (Refereed) Published
Abstract [en]

Tin monosulfide (SnS) is a promising light-absorbing material with weak environmental constraints for application in thin film solar cells. In this paper, we present low-temperature atomic layer deposition (ALD) of high-purity SnS of both cubic and orthorhombic phases. Using tin(II) 2,4-pentanedionate [Sn(acac)(2)] and hydrogen sulfide (H2S) as precursors, controlled growth of the two polymorphs is achieved. Quartz crystal microbalance measurements are used to establish saturated conditions and show that the SnS ALD is self-limiting over temperatures from at least 80 to 160 degrees C. In this temperature window, a stable mass gain of 19 ng cm(-2) cycle(-1) is observed. The SnS thin film crystal structure and morphology undergo significant changes depending on the conditions. High-resolution transmission electron microscopy and X-ray diffraction demonstrate that fully saturated growth requires a large H2S dose and results in the cubic phase. Smaller H2S doses and higher temperatures favor the orthorhombic phase. The optical properties of the two polymorphs differ significantly, as demonstrated by spectroscopic ellipsometry. The orthorhombic phase displays a wide (0.3-0.4 eV) Urbach tail in the near-infrared region, ascribed to its nanoscale structural disorder and/or to sulfur vacancy-induced gap states. In contrast, the cubic phase is smooth and void-free and shows a well-defined, direct forbidden-type bandgap of 1.64 eV.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2017
National Category
Chemical Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-321836 (URN)10.1021/acs.chemmater.6b05323 (DOI)000399264100042 ()
Funder
Swedish Research Council, 621-2014-5599
Available from: 2017-05-15 Created: 2017-05-15 Last updated: 2017-05-15Bibliographically approved
Projects
ARCIGS-M; Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics; Publications
Donzel-Gargand, O., Thersleff, T., Keller, J., Törndahl, T., Larsson, F., Wallin, E., . . . Edoff, M. (2018). Deep surface Cu depletion induced by K in high-efficiency Cu(In,Ga)Se2 solar cell absorbers. Progress in PhotovoltaicsSalome, P. M. P., Vermang, B., Ribeiro-Andrade, R., Teixeira, J. P., Cunha, J. M. V., Mendes, M. J., . . . Sadewasser, S. (2018). Passivation of Interfaces in Thin Film Solar Cells: Understanding the Effects of a Nanostructured Rear Point Contact Layer. Advanced Materials Interfaces, 5(2), Article ID 1701101. Kotipalli, R., Poncelet, O., Li, G., Zeng, Y., Francis, L., Vermang, B. & Flandre, D. (2017). Addressing the impact of rear surface passivation mechanisms on ultra-thin Cu(In,Ga)Se2 solar cell performances using SCAPS 1-D model. Solar Energy, 157, 603-613, Article ID 1708055. Goffard, J., Colin, C., Mollica, F., Cattoni, A., Sauvan, C., Lalanne, P., . . . Collin, S. (2017). Light Trapping in Ultrathin CIGS Solar Cells withNanostructured Back Mirrors. IEEE JOURNAL OF PHOTOVOLTAICS, 7(5), 1433-1441, Article ID 2156-3381. Poncelet, O., Kotipalli, R., Vermang, B., Macleod, A., Francis, L. A. & Flandre, D. (2017). Optimisation of rear reflectance in ultra-thin CIGS solar cells towards>20% efficiency. Solar Energy, 146, 443-452
Organisations
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ORCID iD: ORCID iD iconorcid.org/0000-0003-4111-4613

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