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  • 1. Apell, S. P.
    et al.
    Hanson, G. W.
    Hägglund, Carl
    epartment of Chemical Engineering, Stanford University, USA.
    High optical absorption in grapheneManuscript (preprint) (Other academic)
  • 2. Bakke, J.
    et al.
    Hägglund, Carl
    Stanford University, Stanford, California, USA.
    Jung, H. J.
    Sinclair, R.
    Bent, S.
    Atomic layer deposition of CdO and CdxZn1−xO films2013In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 140, no 2-3, p. 465-471Article in journal (Refereed)
  • 3. Bakke, J.
    et al.
    Tanskanen, J.
    Hägglund, Carl
    Stanford University, Stanford, California, USA.
    Pakkanen, T.
    Bent, S.
    Growth characteristics, material properties, and optical properties of zinc oxysulfide films deposited by atomic layer deposition2012In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 30, p. 01A135-Article in journal (Refereed)
  • 4.
    Bakke, Jonathan R.
    et al.
    Stanford University.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Stanford University.
    Hee Joon, Jung
    Stanford University.
    Sinclair, Robert
    Stanford University.
    Bent, Stacey F.
    Stanford University.
    Graded and alloyed II-VI semiconductors for photovoltaic buffer layers grown by atomic layer deposition (ALD)2011Conference paper (Refereed)
  • 5.
    Bilousov, Oleksandr V.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ren, Yi
    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.
    Donzel-Gargand, Olivier
    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.
    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.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    ALD of phase controlled tin monosulfide thin films2017Conference paper (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.

  • 6.
    Bilousov, Oleksandr V.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ren, Yi
    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.
    Donzel-Gargand, Olivier
    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.
    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.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Atomic Layer Deposition of Cubic and Orthorhombic Phase Tin Monosulfide2017In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, no 7, p. 2969-2978Article in journal (Refereed)
    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.

  • 7.
    Edoff, Marika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Joel, Jonathan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Vermang, Bart
    IMEC, Kapeldreef 75, B-3001 Leuven, Belgium..
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Back Contact Passivation Effects in Bi-Facial Thin CIGS Solar Cells2016In: 2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC), IEEE , 2016, p. 3527-3529Conference paper (Refereed)
    Abstract [en]

    Bi-facial solar cells with ultrathin CIGS solar cells are fabricated to investigate the influence of back contact passivation. Solar cells with CIGS thicknesses of 300 and 500 nm and with an ultrathin transparent Mo layer are characterized using EQE measurements from both the front and the rear side as well as with I-V measurements. Back contact passivation consisting of Al2O3 deposited by atomic layer deposition and nano-sized point contact openings is used. The results are compared to cells with only the transparent Mo layer as back contact. We find a significant effect of the passivation manifested as an increase in the current density of the solar cells with the passivation.

  • 8.
    Ericson, Tove
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Larsson, Fredrik
    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.
    Frisk, Christopher
    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.
    Kosyak, Volodymyr
    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.
    Li, Shuyi
    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.
    Zinc-Tin-Oxide Buffer Layer and Low Temperature Post Annealing Resulting in a 9.0% Efficient Cd-Free Cu2ZnSnS4 Solar Cell2017In: Solar RRL, ISSN 2367-198X, Vol. 1, no 5, article id 1700001Article in journal (Refereed)
    Abstract [en]

    Zn1−xSnxOy (ZTO) has yielded promising results as a buffer material for the full sulfur Cu2ZnSnS4 (CZTS), with efficiencies continuously surpassing its CdS-references. ZTO can be deposited by atomic layer deposition (ALD), enabling tuning of the conduction band position through the choice of metal ratio or deposition temperature. Thus, an optimization of the conduction band alignment between ZTO and CZTS can be achieved. The ZTO bandgap is generally larger than that of CdS and can therefore yield higher currents due to reduced losses in the short wavelength region. Another advantage is the possibility to omit the toxic Cd. In this study, the ALD process temperature was varied from 105 to 165 °C. Current-blocked devices were obtained at 105 °C, while the highest open-circuit voltage and device efficiency was achieved for 145 °C. The highest fill factor was seen at 165 °C. The best efficiency reached in this study was 9.0%, which, to our knowledge, is the highest efficiency reported for Cd-free full-sulfur CZTS. We also show that the effect of heat needs to be taken into account. The results indicate that part of the device improvement comes from heating the absorber, but that the benefit of using a ZTO-buffer is clear.

  • 9. Gusak, Viktoria
    et al.
    Kasemo, B.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Chalmers University of Technology.
    Nanoparticle plasmon induced light absorption in ultrathin a-Si2012Conference paper (Refereed)
  • 10. Gusak, Viktoria
    et al.
    Kasemo, Bengt
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    High aspect ratio plasmonic nanocones for enhanced light absorption in ultrathin amorphous silicon films2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 40, p. 22840-22846Article in journal (Refereed)
  • 11.
    Gusak, Viktoria
    et al.
    Chalmers University of Technology.
    Kasemo, Bengt
    Chalmers University of Technology.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Chalmers University of Technology.
    Thickness dependence of plasmonic charge carrier generation in ultrathin a-Si:H layers for solar cells2011In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 5, no 8, p. 6218-6225Article in journal (Refereed)
  • 12.
    Hagglund, C
    et al.
    Chalmers University of Technology.
    Kasemo, B
    Chalmers University of Technology.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    In situ reactivity and FTIR study of the wet and dry photooxidation of propane on anatase TiO22005In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 21, p. 10886-10895Article in journal (Refereed)
    Abstract [en]

    The photocatalytic oxidation (PCO) of trace amounts of propane (500 ppm) on nanocrystalline anatase TiO2 has been investigated in situ as a function of temperature (T = 318-473 K), humidity (C-H2O = 0-4%), and time by means of mass spectrometry and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). Propane adsorbs associatively on TiO2 at 318 K in dry air, while at 473 K small amounts of thermal dissociation products appear on the surface. In agreement with previous studies, propane is found primarily to be converted to acetone by reactions with photogenerated oxygen radicals. Various successive reaction paths exist, where the branching depends on the temperature and hydroxylation state of the surface. Under dry conditions at 318 K, acetone oxidation is initially kinetically hindered, while, above 400 K, acetone readily decomposes. The thermally assisted reaction channel leads to detrimental bonding of surface species and inhibition of the catalytic activity. It is manifested by a coloration of the sample and suggested to be coupled to surface reduction. Under humidified conditions, there is an optimum of the PCO in C-H2O and T space, which is estimated to correspond to an equilibrium coverage of one monolayer of H2O (or bilayer). The latter reaction condition also corresponds to sustained high propane conversion and is characterized by rapid establishment of steady state rates. The optimum PCO is discussed in terms of a balance between (i) sustaining enough of a photoactive water monolayer to avoid detrimental bonding of surface species, (ii) allowing reactants to adsorb and access bulk TiO2 photoexcitations, and at the same time (iii) maximizing the thermally assisted decomposition of intermediates.

  • 13.
    Hinnemo, Malkolm
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ahlberg, Patrik
    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.
    Ren, Wencai
    Institute of Metal Research, Chinese Academy of Sciences.
    Cheng, Hui-Ming
    Institute of Metal Research, Chinese Academy of Sciences.
    Zhang, Shi-Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zhang, Zhi-Bin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Scalable residue-free graphene for surface-enhanced Raman scattering2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 98, p. 567-571Article in journal (Refereed)
    Abstract [en]

    A room-temperature polymer-assisted transfer process is developed for large-area, single-layer graphene grown by means of chemical vapor deposition (CVD). This process leads to transferred graphene layers free of polymer contamination. The absence of polymer residues boosts the surface-enhanced Raman scattering (SERS) of the CVD graphene with gold nanoparticles (Au NPs) deposited atop by evaporation. The SERS enhancement of the CVD graphene reaches similar to 120 for the characteristic 2D peak of graphene, the highest enhancement factor achieved to date, when the Au NPs are at the threshold of percolation. Our simulation supported by experiment suggests that the polymer residues persistently present on the graphene transferred by the conventional polymer-assisted method are equivalent to an ultrathin film of less than 1 nm thickness. The presence of polymer residues drastically reduces SERS due to the separation of the Au NPs from the underlying graphene. The scalability of CVD graphene opens up for the possibility of graphene-based SERS sensors.

  • 14.
    Hinnemo, Malkolm
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ahlberg, Patrik
    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.
    Zhang, Shi-Li
    Zhang, Zhi-Bin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Surface-Enhanced Raman Scattering of Graphene with and without Residues2015Conference paper (Other academic)
  • 15.
    Hinnemo, Malkolm
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zhao, Jie
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ahlberg, Patrik
    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.
    Djurberg, Viktor
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Scheicher, Ralph H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Zhang, Shi-Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zhang, Zhi-Bin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    On Monolayer Formation of Pyrenebutyric Acid on Graphene2017In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, no 15, p. 3588-3593Article in journal (Refereed)
    Abstract [en]

    As a two-dimensional material with high charge carrier mobility, graphene may offer ultrahigh sensitivity in biosensing. To realize this, the first step is to functionalize the graphene. This is commonly done by using 1-pyrenebutyric acid (PBA) as a linker for biornolecules. However, the adsorption of PBA on graphene remains poorly understood despite reports of successful biosensors functionalized via this route. Here, the PBA adsorption on graphene is characterized through a combination of Raman spectroscopy, ab initio calculations, and spectroscopic ellipsometry. The PBA molecules are found to form a self-assembled monolayer on graphene, the formation of which is self-limiting and Langmuirian. Intriguingly, in concentrated solutions, the PBA molecules are found to stand up and stack horizontally with their edges contacting the graphene surface. This morphology could facilitate a surface densely populated with carboxylic functional groups. Spectroscopic analyses show that the monolayer saturates at 5.3 PBA molecules per nm(2) and measures similar to 0.7 nm in thickness. The morphology study of this PBA monolayer sheds light on the pi-pi stacking of small-molecule systems on graphene and provides an excellent base for optimizing functionalization procedures.

  • 16.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Strongly coupled plasmon-nanocavity modes for broadband, near-field induced absorption in ultrathin semiconductor coatings2015In: Part of Proceedings of SPIE Vol. 9547 Plasmonics: Metallic Nanostructures and Their Optical Properties XIII, San Diego, California, USA: SPIE - International Society for Optical Engineering, 2015Conference paper (Refereed)
  • 17.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ultrathin metal-semiconductor nanocomposites as resource efficient light absorbers for photovoltaics2014Conference paper (Refereed)
    Abstract [en]

    The light absorbing semiconductor layers of solar cells are traditionally made to absorb nearly all photons with energies exceeding the bandgap, more or less through choice of thickness according to the inverse of the absorption coefficient. A drastically different approach is to design a nanocomposite material with effective optical constants such that they approach the ideal conditions for light absorption for a given, very small thickness. By combining semiconducting layers suitable for solar energy conversion with noble metal nanoparticles supporting localized surface plasmon resonances in the visible to near infrared range, it has been theoretically and experimentally demonstrated that such conditions can readily be accomplished with mass equivalent thicknesses on the nanoscale. Effective absorption coefficients exceeding 1 nm-1, or an order of magnitude higher than for bulk metals, were observed.1 In order to exploit the light absorption in such nanocomposites for efficient solar energy conversion, several important challenges must be successfully addressed. Firstly, the absorption must cover a broad spectral range, typically between 2 and 3 eV in width depending on bandgap. Further, losses in the form of Joule heating of the metal component must be minimized. Finally, efficient charge carrier separation must be accomplished. One approach that may prove useful in these regards is to exploit plasmon near-field induced absorption in a strongly coupled, highly damped semiconductor material.2 A high damping of the plasmon resonance both broadens the absorption peak and causes a high fraction of the absorption to take place in the semiconductor layer, thus avoiding Joule heating and producing more long lived electron hole pairs that can feasibly be separated with higher yield. Recent experimental results in this area, based on ultrathin semiconductor layers grown on metal nanoparticle arrays by atomic layer deposition, will be presented.

     

    1          Hägglund, C., Zeltzer, G., Ruiz, R., Thomann, I., Lee, H.-B.-R., Brongersma, M. L. & Bent, S. F. Self-assembly based plasmonic arrays tuned by atomic layer deposition for extreme visible light absorption. Nano Lett. 13, 3352-3357 (2013). DOI: 10.1021/nl401641v

    2          Hägglund, C. & Apell, S. P. Plasmonic near-field absorbers for ultrathin solar cells. The Journal of Physical Chemistry Letters 3, 1275-1285 (2012). DOI: 10.1021/jz300290d

  • 18.
    Hägglund, Carl
    et al.
    Stanford University, Stanford, California, USA.
    Apell, P.
    Plasmonic near-field absorbers for ultrathin solar cells2012In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 3, no 10, p. 1275-1285Article in journal (Refereed)
  • 19.
    Hägglund, Carl
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Department of Applied Physics, Chalmers University of Technology.
    Apell, Peter S.
    Department of Applied Physics, Chalmers University of Technology.
    Kasemo, Bengt
    Department of Applied Physics, Chalmers University of Technology.
    Maximized optical absorption in ultrathin films and its application to plasmon-based two-dimensional photovoltaics2010In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 10, no 8, p. 3135-3141Article in journal (Refereed)
  • 20.
    Hägglund, Carl
    et al.
    Department of Applied Physics, Chalmers University of Technology.
    Apell, Peter S.
    Department of Applied Physics, Chalmers University of Technology.
    Kasemo, Bengt
    Department of Applied Physics, Chalmers University of Technology.
    Maximized optical absorption in ultrathin films and its application to plasmon-based two-dimensional photovoltaics (vol 10, pg 3135, 2010)2011In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 11, no 2, p. 915-916Article in journal (Refereed)
  • 21.
    Hägglund, Carl
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Chalmers University of Technology.
    Apell, S. P.
    Chalmers University of Technology.
    Resource efficient plasmon-based 2D-photovoltaics with reflective support2010In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 18, no S3, p. A343-A356Article in journal (Refereed)
  • 22.
    Hägglund, Carl
    et al.
    Stanford University, Stanford, California, USA.
    Bent, Stacey F.
    Stanford University, Stanford, California, USA.
    Ultrathin light absorbers based on plasmonic nanocomposites2013In: SPIE Newsroom, ISSN 1818-2259Article in journal (Other (popular science, discussion, etc.))
  • 23.
    Hägglund, Carl
    et al.
    Stanford University.
    Grehl, Thomas
    ION-TOF GmbH.
    Tanskanen, Jukka T.
    Stanford University.
    Yee, Ye Sheng
    Stanford University.
    Mullings, Marja N.
    Stanford University.
    Clemens, Bruce M.
    Stanford University.
    Brongersma, Hidde H.
    ION-TOF GmbH.
    Bent, Stacey F.
    Stanford University.
    Atomic layer deposition of thin film laminates and solid solutions – the case of zinc tin oxide2013Conference paper (Refereed)
  • 24.
    Hägglund, Carl
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Stanford Univ, Dept Chem Engn, Stanford, CA 94305 USA.
    Grehl, Thomas
    Tanskanen, Jukka T.
    Yee, Ye Sheng
    Mullings, Marja N.
    Mackus, Adriaan J. M.
    MacIsaac, Callisto
    Clemens, Bruce M.
    Brongersma, Hidde H.
    Bent, Stacey F.
    Growth, intermixing, and surface phase formation for zinc tin oxide nanolaminates produced by atomic layer deposition2016In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 34, no 2, article id 021516Article in journal (Refereed)
    Abstract [en]

    A broad and expanding range of materials can be produced by atomic layer deposition at relatively low temperatures, including both oxides and metals. For many applications of interest, however, it is desirable to grow more tailored and complex materials such as semiconductors with a certain doping, mixed oxides, and metallic alloys. How well such mixed materials can be accomplished with ALD requires knowledge of the conditions under which the resulting films will be mixed, solid solutions, or laminated. The growth and lamination of zinc oxide and tin oxide is studied here by means of the extremely surface sensitive technique of low energy ion scattering, combined with bulk composition and thickness determination, and X-ray diffraction. At the low temperatures used for deposition (150 °C) there is little evidence for atomic scale mixing even with the smallest possible bilayer period, and instead a morphology with small ZnO inclusions in a SnOx matrix is deduced. Post-annealing of such laminates above 400 °C however produces a stable surface phase with a 30% increased density. From the surface stoichiometry, this is likely the inverted spinel of zinc stannate, Zn2SnO4. Annealing to 800 °C results in films containing crystalline Zn2SnO4, or multilayered films of crystalline ZnO, Zn2SnO4 and SnO2 phases, depending on the bilayer period.

  • 25.
    Hägglund, Carl
    et al.
    Stanford University.
    Zeltzer, G.
    Ruiz, R.
    Thomann, I.
    Lee, H.B.R.
    Brongersma, M.
    Bent, S.
    Self-assembly based plasmonic arrays tuned by atomic layer deposition for extreme visible light absorption2013In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 13, no 7, p. 3352-3357Article in journal (Refereed)
  • 26.
    Hägglund, Carl
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Department of Chemical Engineering, Stanford University, Stanford, California 94305, USA.
    Zeltzer, Gabriel
    HGST, a Western Digital company, San Jose, California 95135, USA.
    Ruiz, Ricardo
    HGST, a Western Digital company, San Jose, California 95135, USA.
    Wangperawong, Artit
    Department of Electrical Engineering, Stanford University, Stanford, California 94305, USA.
    Roelofs, Katherine E.
    Department of Materials Science and Engineering, Stanford University, Stanford, California, 94305, USA.
    Bent, Stacey F.
    Department of Chemical Engineering, Stanford University, Stanford, California 94305, USA.
    Strong coupling of plasmon and nanocavity modes for dual-band, near-perfect absorbers and ultrathin photovoltaics2016In: ACS Photonics, E-ISSN 2330-4022, Vol. 3, no 3, p. 456-463Article in journal (Refereed)
    Abstract [en]

    When optical resonances interact strongly, hybridized modes are formed with mixed properties inherited from the basic modes. Strong coupling therefore tends to equalize properties such as damping and oscillator strength of the spectrally separate resonance modes. This effect is here shown to be very useful for the realization of near perfect dual-band absorption with ultrathin (~10 nm) layers in a simple geometry. Absorber layers are constructed by atomic layer deposition of the heavy-damping semiconductor tin monosulfide (SnS) onto a two-dimensional gold nanodot array. In combination with a thin (55 nm) SiO2 spacer layer and a highly reflective Al film on the back, a semi-open nanocavity is formed. The SnS coated array supports a localized surface plasmon resonance in the vicinity of the lowest order anti-symmetric Fabry-Perot resonance of the nanocavity. Very strong coupling of the two resonances is evident through anti-crossing behavior with a minimum peak splitting of 400 meV, amounting to 24% of the plasmon resonance energy. The mode equalization resulting from this strong interaction enables simultaneous optical impedance matching of the system at both resonances, and thereby two near perfect absorption peaks which together cover a broad spectral range. When paired with the heavy damping from SnS band-to-band transitions, this further enables approximately 60% of normal incident solar photons with energies exceeding the bandgap to be absorbed in the 10 nm SnS coating. Thereby, these results establish a distinct relevance of strong coupling phenomena to efficient, nanoscale photovoltaic absorbers and more generally for fulfilling a specific optical condition at multiple spectral positions.

  • 27.
    Larsen, Jes K
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Li, Shuyi
    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.
    Ren, Yi
    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.
    Heinemann, Marc
    Kretzschmar, Steffen
    Unold, Thomas
    Platzer-Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Interference effects in photoluminescence spectra of Cu2ZnSnS4 and Cu(In,Ga)Se2 thin films2015In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 118, no 3, article id 035307Article in journal (Refereed)
    Abstract [en]

    Photoluminescence (PL) is commonly used for investigations of Cu2ZnSnS(e)4 [CZTS(e)] and Cu(In,Ga)Se2 (CIGS) thin film solar cells. The influence of interference effects on these measurements is, however, largely overlooked in the community. Here, it is demonstrated that PL spectra of typical CZTS absorbers on Mo/glass substrates can be heavily distorted by interference effects. One reason for the pronounced interference in CZTS is the low reabsorption of the PL emission that typically occurs below the band gap. A similar situation occurs in band gap graded CIGS where the PL emission originates predominantly from the band gap minimum located at the notch region. Based on an optical model for interference effects of PL emitted from a thin film, several approaches to reduce the fringing are identified and tested experimentally. These approaches include the use of measured reflectance data, a calculated interference function, use of high angles of incidence during PL measurements as well as the measurement of polarized light near the Brewster angle.

  • 28.
    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.

  • 29.
    Li, Shu-Yi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hagglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ren, Yi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Scragg, Jonathan J. S.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Larsen, Jes K.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Frisk, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Rudisch, Katharina
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Englund, Sven
    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.
    Optical properties of reactively sputtered Cu2ZnSnS4 solar absorbers determined by spectroscopic ellipsometry and spectrophotometry2016In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 149, p. 170-178Article in journal (Refereed)
    Abstract [en]

    We have determined for the first time the device-relevant optical constants of 500 nm and 800 nm-thick Cu2ZnSnS4 absorbers, grown on bare and Mo-coated soda-lime glass (SLG), using spectroscopic ellipsometry (SE). The composition, structure, phase purity and morphology were characterized by X-ray fluorescence, X-ray photoelectron spectroscopy depth profiling, X-ray diffraction, Raman spectroscopy, scanning-electron microscopy and atomic force microscopy. For the SE analysis, carefully determined sample characteristics were utilized to build a multilayer stack optical model, in order to derive the dielectric functions and refractive indices. The SE-derived absorption coefficients from CZTS/SLG samples were compared with those derived from complementary spectrophotometry measurements and found to be in good agreement. The bandgap determined from Tauc plots was E-g=1.57 +/- 0.02 eV. The absorption coefficients just above the bandgap were found to be a few 10(4) cm(-1) and to exceed 10(5) cm(-1) at energies above similar to 2.5 eV, which is much higher than previously found. The sub-bandgap k-value was found to be k similar to 0.05 or less, suggesting that a moderate band tail is present. Separate device characterization performed on identical samples allowed us to assign device efficiencies of, respectively, 2.8% and 5.3% to the 500 nm and 800 nm-thick samples featured in this study.

  • 30.
    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.

  • 31.
    Mazzotta, Francesco
    et al.
    Department of Applied Physics, Chalmers University of Technology.
    Wang, Guoliang
    Department of Applied Physics, Chalmers University of Technology.
    Hägglund, Carl
    Department of Applied Physics, Chalmers University of Technology.
    Höök, Fredrik
    Department of Applied Physics, Chalmers University of Technology.
    Jonsson, Magnus P.
    Department of Applied Physics, Chalmers University of Technology.
    Nanoplasmonic biosensing with on-chip electrical detection2010In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 26, p. 1131-1136Article in journal (Refereed)
  • 32. Methaapanon, R.
    et al.
    Geyer, S. M.
    Hägglund, Carl
    Department of Chemical Engineering, Stanford University, Stanford, California, USA.
    Pianetta, P. A.
    Bent, S. F.
    Portable atomic layer deposition reactor for in situ synchrotron photoemission studies2013In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 84Article in journal (Refereed)
  • 33. Mullings, Marja N.
    et al.
    Bakke, Jonathan R.
    Hägglund, Carl
    Stanford University.
    Bent, Stacey F.
    Stanford University.
    Atomic Layer Deposition of Nanoscale Materials for Energy Conversion2011Conference paper (Refereed)
  • 34. Mullings, Marja N.
    et al.
    Hägglund, Carl
    Department of Chemical Engineering, Stanford University, Stanford, California.
    Bent, Stacey F.
    Tin oxide atomic layer deposition from tetrakis(dimethylamino)tin and water2013In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 31Article in journal (Refereed)
  • 35. Mullings, Marja N.
    et al.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Tanskanen, Jukka T.
    Yee, Yesheng
    Geyer, Scott
    Bent, Stacey F.
    Thin film characterization of zinc tin oxide deposited by thermal atomic layer deposition2014In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 556, p. 186-Article in journal (Refereed)
  • 36.
    Sendler, Jan
    et al.
    Univ Luxembourg, Phys & Mat Sci Res Unit, Lab Photovolta, 41 Rue Brill, L-4422 Belvaux, Luxembourg..
    Thevenin, Maxime
    Univ Luxembourg, Phys & Mat Sci Res Unit, Lab Photovolta, 41 Rue Brill, L-4422 Belvaux, Luxembourg..
    Werner, Florian
    Univ Luxembourg, Phys & Mat Sci Res Unit, Lab Photovolta, 41 Rue Brill, L-4422 Belvaux, Luxembourg..
    Redinger, Alex
    Univ Luxembourg, Phys & Mat Sci Res Unit, Lab Photovolta, 41 Rue Brill, L-4422 Belvaux, Luxembourg.;Helmholtz Zentrum Mat & Energie GmbH, Hahn Meitner Pl 1, D-14109 Berlin, Germany..
    Li, Shuyi
    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.
    Platzer-Björkman, Charlotte
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Siebentritt, Susanne
    Univ Luxembourg, Phys & Mat Sci Res Unit, Lab Photovolta, 41 Rue Brill, L-4422 Belvaux, Luxembourg..
    Photoluminescence studies in epitaxial CZTSe thin films2016In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 120, no 12, article id 125701Article in journal (Refereed)
    Abstract [en]

    Epitaxial Cu2ZnSnSe4 (CZTSe) thin films were grown by molecular beam epitaxy on GaAs(001) using two different growth processes, one containing an in-situ annealing stage as used for solar cell absorbers and one for which this step was omitted. Photoluminescences (PL) measurements carried out on these samples show no dependence of the emission shape on the excitation intensity at different temperatures ranging from 4K to 300 K. To describe the PL measurements, we employ a model with fluctuating band edges in which the density of states of the resulting tail states does not seem to depend on the excited charge carrier density. In this interpretation, the PL measurements show that the annealing stage removes a defect level, which is present in the samples without this annealing.

  • 37. Tanskanen, Jukka T.
    et al.
    Bakke, Jonathan R.
    Hägglund, Carl
    Stanford University.
    Pakkanen, Tapani A.
    Bent, Stacey F.
    Bandgap engineering of ternary ZnOxS1-x CdxZn1-xO thin films via atomic layer deposition2012Conference paper (Refereed)
  • 38. Tanskanen, Jukka T.
    et al.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Bent, Stacey F.
    Correlating growth characteristics in atomic layer deposition with precursor molecular structure: the case of zinc tin oxide2014In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 26, no 9, p. 2895-2802Article in journal (Refereed)
  • 39. Wangperawong, Artit
    et al.
    Herron, Steven M.
    Hägglund, Carl
    Stanford University.
    Bent, Stacey F.
    Cheap and Thin: Two Processing Approaches to Manufacturable Solar Cells2012Conference paper (Refereed)
  • 40.
    Wangperawong, Artit
    et al.
    Stanford University, Stanford, California, USA.
    Herron, Steven M.
    Stanford University, Stanford, California, USA.
    Runser, Rory R.
    University of California at Berkeley, Berkeley, California, USA .
    Hägglund, Carl
    Stanford University, Stanford, California, USA.
    Tanskanen, Jukka T.
    Stanford University, Stanford, California, USA.
    Lee, Han-Bo-Ram
    Incheon National University, Yeonsu-gu, Incheon, South Korea .
    Clemens, Bruce M.
    Stanford University, Stanford, California, USA.
    Bent, Stacey F.
    Stanford University, Stanford, California, USA.
    Vapor transport deposition and epitaxy of orthorhombic SnS on glass and NaCl substrates2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, no 5Article in journal (Refereed)
  • 41. Wangperawong, Artit
    et al.
    Hägglund, Carl
    Stanford University, USA.
    Bent, Stacey F
    Optical response of 3D nano-architecture solar cells and integration with 3D device physics2011In: Next Generation (Nano) Photonic and Cell Technologies For Solar Energy Conversion II, San Diego, CA: SPIE - International Society for Optical Engineering, 2011, p. 81110R-Conference paper (Refereed)
    Abstract [en]

    We study the optical response of various nanojunction solar cell architectures and examine how various cylindrical arrangements of emitter, base, glass and transparent conductor affect reflection and absorption of incident light. The photogeneration profiles of such nano-architectures are cylindrically asymmetric, varying axially, radially and azimuthally within the wavelength band investigated. Such 3D profiles require 3D device models for accurate device analysis. The extended nanojunction configuration was examined in more detail, as this design is known to have superior performance. The particular design consists ofnanostructured glass and a superstrate arrangement of the other device elements.

  • 42.
    Zhang, Xiaoliang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Aitola, Kerttu
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Kaskela, Antti
    Aalto Univ, Nanomat Grp, Dept Appl Phys, POB 15100, FI-00076 Espoo, Finland..
    Johansson, Malin B.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sveinbjörnsson, Kári
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Kauppinen, Esko I.
    Aalto Univ, Nanomat Grp, Dept Appl Phys, POB 15100, FI-00076 Espoo, Finland..
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Dry-Deposited Transparent Carbon Nanotube Film as Front Electrode in Colloidal Quantum Dot Solar Cells2017In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 10, no 2, p. 434-441Article in journal (Refereed)
    Abstract [en]

    Single-walled carbon nanotubes (SWCNTs) show great potential as an alternative material for front electrodes in photovoltaic applications, especially for flexible devices. In this work, a press-transferred transparent SWCNT film was utilized as front electrode for colloidal quantum dot solar cells (CQDSCs). The solar cells were fabricated on both glass and flexible substrates, and maximum power conversion efficiencies of 5.5 and 5.6 %, respectively, were achieved, which corresponds to 90 and 92% of an indium-doped tin oxide (ITO)-based device (6.1 %). The SWCNTs are therefore a very good alternative to the ITO-based electrodes especially for flexible solar cells. The optical electric field distribution and optical losses within the devices were simulated theoretically and the results agree with the experimental results. With the optical simulations that were performed it may also be possible to enhance the photovoltaic performance of SWCNT-based solar cells even further by optimizing the device configuration or by using additional optical active layers, thus reducing light reflection of the device and increasing light absorption in the quantum dot layer.

  • 43.
    Zhang, Xiaoliang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Johansson, Erik M.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Electro-Optics of Colloidal Quantum Dot Solids for Thin-FilmSolar Cells2016In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 26, no 8, p. 1253-1260Article, review/survey (Refereed)
    Abstract [en]

    The electro-optics of thin-fi lm stacks within photovoltaic devices playsa critical role for the exciton and charge generation and therefore thephotovoltaic performance. The complex refractive indexes of each layer inheterojunction colloidal quantum dot (CQD) solar cells are measured andthe optical electric fi eld is simulated using the transfer matrix formalism.The exciton generation rate and the photocurrent density as a function ofthe quantum dot solid thickness are calculated and the results from thesimulations are found to agree well with the experimentally determinedresults. It can therefore be concluded that a quantum dot solid may bemodeled with this approach, which is of general interest for this type ofmaterials. Optimization of the CQD solar cell is performed by using theoptical simulations and a maximum solar energy conversion effi ciency of6.5% is reached for a CQD solid thickness of 300 nm.

  • 44.
    Zhang, Xiaoliang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Johansson, Erik M.J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Highly efficient, transparent and stable semitransparent colloidal quantum dot solar cells: a combined numerical modeling and experimental approach2017In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 10, no 1, p. 216-224Article in journal (Refereed)
    Abstract [en]

    Semitransparent solar cells (SSCs) can open new photovoltaic applications in many areas. However, because of the fundamental trade-off between optical transparency and photovoltaic efficiency, it is of special importance to minimize additional optical losses such as from reflectance and parasitic absorption. In this work, a semitransparent colloidal quantum dot solar cell (SCQDSC) with high efficiency, transparency and stability is investigated using a coupled theoretical and experimental approach. Extensive numerical simulations and experimental investigations are performed for optimizing the device transparency and efficiency simultaneously. The results show that the transparency and efficiency are largely enhanced as a result of lowering the optical losses in the SCQDSC, and the device exhibits a high efficiency of 7.3% with an average visible transmittance of 20.4%. Importantly, the SCQDSC exhibits very good stability under long term continuous illumination and the unencapsulated SCQDSCs show no large degradation in performance during storage for 70 days under ambient conditions. These findings suggest that the SCQDSC has high potential for applications, such as for building integrated photovoltaics, automobiles or screens. Moreover, this work also provides practical and quantitative guidelines for further enhancing the SSC performance.

  • 45.
    Zhang, Xiaoliang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Johansson, Malin B
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sveinbjörnsson, Kari
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Johansson, Erik M
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Fine Tuned Nanolayered Metal/Metal Oxide Electrode for Semitransparent Colloidal Quantum Dot Solar Cells2016In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 26, no 12, p. 1921-1929Article in journal (Refereed)
    Abstract [en]

    Semitransparent photovoltaics have great potential, for example, in buildingintegrationor in portable electronics. However, the front and back contactelectrodes signifi cantly affect the light transmission and photovoltaic performanceof the complete device. Herein, the use of a semitransparentnanolayered metal/metal oxide electrode for a semitransparent PbS colloidalquantum dot solar cell to increase the light transmission and power conversioneffi ciency is reported. The effect of the nanolayered electrode on theoptical properties within the solar cells is studied and compared to a theoreticallymodel to identify the origin of optical losses that lower the devicetransmission. The results show that the light transmission in the visibleregion and the photovoltaic performance are signifi cantly enhanced with thenanolayered electrode. The solar cell shows an effi ciency of 5.4% and averagevisible transmittance of 24.1%, which is an increase by 28.6% and 59.6%,respectively, compared to the device with a standard Au fi lm as the electrode.These results demonstrate that the optical and electrical modifi cation oftransparent electrode is possible and essential for reducing the light refl ectionand absorption of the electrode in semitransparent photovoltaics, and,meanwhile the demonstrated nanolayered materials may provide an avenuefor enhancing the device transparency and efficiency.

  • 46.
    Zhang, Xiaoliang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Johansson, Malin B
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sveinbjörnsson, Kári
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Liu, Jianhua
    Beihang Univ, Sch Mat Sci & Engn, Beijing 100191, Peoples R China..
    Johansson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    FTO-free top-illuminated colloidal quantum dot electro-optics in devices2017In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 158, p. 533-542Article in journal (Refereed)
    Abstract [en]

    A solar cell device architecture with top-illumination, where the light does not pass through the substrate, is advantageous for many applications. It is also specifically useful for the construction of tandem or multiple junction photovoltaic devices, with illumination through the top solar cell. Here, a top-illuminated colloidal quantum dot solar cell (TI-CQDSC) is demonstrated and compared with a conventional colloidal quantum dot solar cell (C-CQDSC) constructed on a FTO (fluorine doped tin oxide) glass substrate both theoretically and experimentally. The optical electric field distribution in the solar cells with different configuration is simulated using transfer matrix formalism and a more intense optical electric field was observed in TI-CQDSC, leading to a higher exciton generation rate within the colloidal quantum dot solid. The TI-CQDSCs are constructed on both nonconductive glass and flexible substrates, and a maximum power conversion efficiency of 6.4% and 5.6% is achieved, respectively, comparing to that of 5.9% for the C-CQDSC. The improved performance of the top illuminated solar cell is attributed to a combination of enhanced optical electric field intensity in the colloidal quantum dot solid and superior conductivity of the transparent metal film electrode.

1 - 46 of 46
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