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William N. Shafarman - One of the best experts on this subject based on the ideXlab platform.

  • Reduced Cu(InGa)Se2 Thickness in Solar Cells Using a Superstrate Configuration
    2015
    Co-Authors: William N. Shafarman
    Abstract:

    This project by the Institute of Energy Conversion (IEC) and the Department of Electrical and Computer Engineering at the University of Delaware sought to develop the technology and underlying science to enable reduced cost of Cu(InGa)Se2 manufacturing by reducing the thickness of the Cu(InGa)Se2 absorber layer by half compared to typical production. The approach to achieve this was to use the Superstrate cell Configuration in which light is incident on the cell through the glass. This structure facilitates optical enhancement approaches needed to achieve high efficiency with Cu(InGa)Se2 thicknesses less than 1 µm. The primary objective was to demonstrate a Cu(InGa)Se2 cell with absorber thickness 0.5 - 0.7 µm and 17% efficiency, along with a quantitative loss analysis to define a pathway to 20% efficiency. Additional objectives were the development of stable TCO and buffer layers or contact layers to withstand the Cu(InGa)Se2 deposition temperature and of advanced optical enhancement methods. The underlying fundamental science needed to effectively transition these outcomes to large scale was addressed by extensive materials and device characterization and by development of comprehensive optical models. Two different Superstrate Configurations have been investigated. A frontwall cell is illuminated through the glass to the primary front junction ofmore » the device. This Configuration has been used for previous efforts on Superstrate Cu(InGa)Se2 but performance has been limited by interdiffusion or reaction with CdS or other buffer layers. In this project, several approaches to overcome these limitations were explored using CdS, ZnO and ZnSe buffer layers. In each case, mechanisms that limit device performance were identified using detailed characterization of the materials and junctions. Due to the junction formation difficulties, efforts were concentrated on a new backwall Configuration in which light is incident through the substrate into the back of the absorber layer. The primary junction is then formed after Cu(InGa)Se2 deposition. This allows the potential benefits of Superstrate cells for optical enhancement while maintaining processing advantages of the substrate Configuration and avoiding the harmful effects of high temperature deposition on p-n junction formation. Backwall devices have outperformed substrate cells at absorber thicknesses of 0.1-0.5 µm through enhanced JSC due to easy incorporation of a Ag reflector and, with light incident on the absorber, the elimination of parasitic absorption in the CdS buffer. An efficiency of 9.7% has been achieved for a backwall Cu(InGa)Se2 device with absorber thickness ~0.4 μm. A critical achievement that enabled implementation of the backwall cell was the development of a transparent back contact using MoO3 or WO3. Processes for controlled deposition of each material by reactive rf sputtering from metal targets were developed. These contacts have wide bandgaps making them well-suited for application as contacts for backwall devices as well as potential use in bifacial cells and as the top cell of tandem CuInSe2-based devices. Optical enhancement will be critical for further improvements. Wet chemical texturing of ZnO films has been developed for a simple, low cost light-trapping scheme for backwall Superstrate devices to enhance long wavelength quantum efficiency. An aqueous oxalic acid etch was developed and found to strongly texture sputtered ZnO with high haze ≈ 0.9 observed across the whole spectrum. And finally, advanced optical models have been developed to assist the characterization and optimization of Cu(InGa)Se2 cells with thin absorbers« less

  • improved performance of ultrathin cu inga se _ bf 2 solar cells with a backwall Superstrate Configuration
    IEEE Journal of Photovoltaics, 2014
    Co-Authors: Hamed Simchi, Jes K Larsen, Kihwan Kim, William N. Shafarman
    Abstract:

    A backwall Superstrate device structure that outperforms conventional substrate Cu(In,Ga)Se 2 devices for thin absorbers is described. The backwall structure of glass/ITO/MoO 3 /Cu(In,Ga)Se 2 /CdS/i-ZnO/Ag utilizes a MoO 3 transparent back contact to allow illumination of the device from the back. The device performance has been improved by modifying the Cu(In,Ga)Se 2 , including alloying with Ag to form (AgCu)(InGa)Se 2 absorber layers. In addition, sulfized back contacts including ITO-S and MoS 2 are compared. Interface properties are discussed based on the XPS analysis and thermodynamics of reactions.

  • Backwall Superstrate Configuration for ultrathin Cu(In,Ga)Se2 solar cells
    Applied Physics Letters, 2014
    Co-Authors: Jes K Larsen, Hamed Simchi, Peipei Xin, Kihwan Kim, William N. Shafarman
    Abstract:

    A backwall Superstrate device structure that outperforms conventional substrate Cu(In,Ga)Se2 devices for thin absorbers is demonstrated. The backwall structure (glass/In2O3-SnO2/MoO3-x/Cu(In,Ga)Se2/CdS/i-ZnO/Ag) utilizes a MoO3−x transparent back contact to allow illumination of the device from the back. In combination with a silver front reflector this cell structure is tailored to enhance performance of devices with submicron thick absorbers. It was found that devices with the backwall Configuration outperform substrate devices in the absorber thickness range dCIGS = 0.1-0.5 μm. The advantage of the backwall Configuration is mainly through superior JSC, achieved by application of a front reflector and elimination of parasitic absorption in CdS.

  • Improved Performance of Ultrathin Cu(InGa)Se $_{\bf 2}$ Solar Cells With a Backwall Superstrate Configuration
    IEEE Journal of Photovoltaics, 2014
    Co-Authors: Hamed Simchi, Jes K Larsen, Kihwan Kim, William N. Shafarman
    Abstract:

    A backwall Superstrate device structure that outperforms conventional substrate Cu(In,Ga)Se 2 devices for thin absorbers is described. The backwall structure of glass/ITO/MoO 3 /Cu(In,Ga)Se 2 /CdS/i-ZnO/Ag utilizes a MoO 3 transparent back contact to allow illumination of the device from the back. The device performance has been improved by modifying the Cu(In,Ga)Se 2 , including alloying with Ag to form (AgCu)(InGa)Se 2 absorber layers. In addition, sulfized back contacts including ITO-S and MoS 2 are compared. Interface properties are discussed based on the XPS analysis and thermodynamics of reactions.

  • Formation of Ga_2O_3 barrier layer in Cu(InGa)Se_2 Superstrate devices with ZnO buffer layer
    MRS Online Proceedings Library, 2013
    Co-Authors: Jes K Larsen, Peipei Xin, William N. Shafarman
    Abstract:

    The junction formation when Cu(InGa)Se_2 is deposited onto ZnO in a Superstrate Configuration (glass/window/buffer/Cu(InGa)Se_2/contact) is investigated by x-ray photoelectron spectroscopy and analysis of device behavior. When Cu(InGa)Se_2 is deposited on ZnO, a Ga_2O_3 layer is formed at the interface. Approaches to avoid the formation of this unfavorable interlayer are investigated. This includes modifications of the process to reduce the thermal load during deposition and improvement of the thermal stability of the ZnO buffer layer. It was demonstrated that both lowering of the substrate deposition temperature and deposition of the ZnO buffer layer at elevated temperature limits the Ga_2O_3 formation. The presence of Ga_2O_3 at the junction does affect the device behavior, resulting in a kink in JV curves measured under illumination. This behavior is absent in devices with limited Ga_2O_3 formation.

Jes K Larsen - One of the best experts on this subject based on the ideXlab platform.

  • improved performance of ultrathin cu inga se _ bf 2 solar cells with a backwall Superstrate Configuration
    IEEE Journal of Photovoltaics, 2014
    Co-Authors: Hamed Simchi, Jes K Larsen, Kihwan Kim, William N. Shafarman
    Abstract:

    A backwall Superstrate device structure that outperforms conventional substrate Cu(In,Ga)Se 2 devices for thin absorbers is described. The backwall structure of glass/ITO/MoO 3 /Cu(In,Ga)Se 2 /CdS/i-ZnO/Ag utilizes a MoO 3 transparent back contact to allow illumination of the device from the back. The device performance has been improved by modifying the Cu(In,Ga)Se 2 , including alloying with Ag to form (AgCu)(InGa)Se 2 absorber layers. In addition, sulfized back contacts including ITO-S and MoS 2 are compared. Interface properties are discussed based on the XPS analysis and thermodynamics of reactions.

  • Backwall Superstrate Configuration for ultrathin Cu(In,Ga)Se2 solar cells
    Applied Physics Letters, 2014
    Co-Authors: Jes K Larsen, Hamed Simchi, Peipei Xin, Kihwan Kim, William N. Shafarman
    Abstract:

    A backwall Superstrate device structure that outperforms conventional substrate Cu(In,Ga)Se2 devices for thin absorbers is demonstrated. The backwall structure (glass/In2O3-SnO2/MoO3-x/Cu(In,Ga)Se2/CdS/i-ZnO/Ag) utilizes a MoO3−x transparent back contact to allow illumination of the device from the back. In combination with a silver front reflector this cell structure is tailored to enhance performance of devices with submicron thick absorbers. It was found that devices with the backwall Configuration outperform substrate devices in the absorber thickness range dCIGS = 0.1-0.5 μm. The advantage of the backwall Configuration is mainly through superior JSC, achieved by application of a front reflector and elimination of parasitic absorption in CdS.

  • Improved Performance of Ultrathin Cu(InGa)Se $_{\bf 2}$ Solar Cells With a Backwall Superstrate Configuration
    IEEE Journal of Photovoltaics, 2014
    Co-Authors: Hamed Simchi, Jes K Larsen, Kihwan Kim, William N. Shafarman
    Abstract:

    A backwall Superstrate device structure that outperforms conventional substrate Cu(In,Ga)Se 2 devices for thin absorbers is described. The backwall structure of glass/ITO/MoO 3 /Cu(In,Ga)Se 2 /CdS/i-ZnO/Ag utilizes a MoO 3 transparent back contact to allow illumination of the device from the back. The device performance has been improved by modifying the Cu(In,Ga)Se 2 , including alloying with Ag to form (AgCu)(InGa)Se 2 absorber layers. In addition, sulfized back contacts including ITO-S and MoS 2 are compared. Interface properties are discussed based on the XPS analysis and thermodynamics of reactions.

  • Formation of Ga_2O_3 barrier layer in Cu(InGa)Se_2 Superstrate devices with ZnO buffer layer
    MRS Online Proceedings Library, 2013
    Co-Authors: Jes K Larsen, Peipei Xin, William N. Shafarman
    Abstract:

    The junction formation when Cu(InGa)Se_2 is deposited onto ZnO in a Superstrate Configuration (glass/window/buffer/Cu(InGa)Se_2/contact) is investigated by x-ray photoelectron spectroscopy and analysis of device behavior. When Cu(InGa)Se_2 is deposited on ZnO, a Ga_2O_3 layer is formed at the interface. Approaches to avoid the formation of this unfavorable interlayer are investigated. This includes modifications of the process to reduce the thermal load during deposition and improvement of the thermal stability of the ZnO buffer layer. It was demonstrated that both lowering of the substrate deposition temperature and deposition of the ZnO buffer layer at elevated temperature limits the Ga_2O_3 formation. The presence of Ga_2O_3 at the junction does affect the device behavior, resulting in a kink in JV curves measured under illumination. This behavior is absent in devices with limited Ga_2O_3 formation.

  • Formation of Ga2O3 barrier layer in Cu (InGa) Se2 Superstrate devices with ZnO buffer layer
    MRS Proceedings, 2013
    Co-Authors: Jes K Larsen, William N. Shafarman
    Abstract:

    The junction formation when Cu(InGa)Se2 is deposited onto ZnO in a Superstrate Configuration (glass/window/buffer/Cu(InGa)Se2/contact) is investigated by x-ray photoelectron spectroscopy and analysis of device behavior. When Cu(InGa)Se2 is deposited on ZnO, a Ga2O3 layer is formed at the interface. Approaches to avoid the formation of this unfavorable interlayer are investigated. This includes modifications of the process to reduce the thermal load during deposition and improvement of the thermal stability of the ZnO buffer layer. It was demonstrated that both lowering of the substrate deposition temperature and deposition of the ZnO buffer layer at elevated temperature limits the Ga2O3 formation. The presence of Ga2O3 at the junction does affect the device behavior, resulting in a kink in JV curves measured under illumination. This behavior is absent in devices with limited Ga2O3 formation.

Hamed Simchi - One of the best experts on this subject based on the ideXlab platform.

  • improved performance of ultrathin cu inga se _ bf 2 solar cells with a backwall Superstrate Configuration
    IEEE Journal of Photovoltaics, 2014
    Co-Authors: Hamed Simchi, Jes K Larsen, Kihwan Kim, William N. Shafarman
    Abstract:

    A backwall Superstrate device structure that outperforms conventional substrate Cu(In,Ga)Se 2 devices for thin absorbers is described. The backwall structure of glass/ITO/MoO 3 /Cu(In,Ga)Se 2 /CdS/i-ZnO/Ag utilizes a MoO 3 transparent back contact to allow illumination of the device from the back. The device performance has been improved by modifying the Cu(In,Ga)Se 2 , including alloying with Ag to form (AgCu)(InGa)Se 2 absorber layers. In addition, sulfized back contacts including ITO-S and MoS 2 are compared. Interface properties are discussed based on the XPS analysis and thermodynamics of reactions.

  • Backwall Superstrate Configuration for ultrathin Cu(In,Ga)Se2 solar cells
    Applied Physics Letters, 2014
    Co-Authors: Jes K Larsen, Hamed Simchi, Peipei Xin, Kihwan Kim, William N. Shafarman
    Abstract:

    A backwall Superstrate device structure that outperforms conventional substrate Cu(In,Ga)Se2 devices for thin absorbers is demonstrated. The backwall structure (glass/In2O3-SnO2/MoO3-x/Cu(In,Ga)Se2/CdS/i-ZnO/Ag) utilizes a MoO3−x transparent back contact to allow illumination of the device from the back. In combination with a silver front reflector this cell structure is tailored to enhance performance of devices with submicron thick absorbers. It was found that devices with the backwall Configuration outperform substrate devices in the absorber thickness range dCIGS = 0.1-0.5 μm. The advantage of the backwall Configuration is mainly through superior JSC, achieved by application of a front reflector and elimination of parasitic absorption in CdS.

  • Improved Performance of Ultrathin Cu(InGa)Se $_{\bf 2}$ Solar Cells With a Backwall Superstrate Configuration
    IEEE Journal of Photovoltaics, 2014
    Co-Authors: Hamed Simchi, Jes K Larsen, Kihwan Kim, William N. Shafarman
    Abstract:

    A backwall Superstrate device structure that outperforms conventional substrate Cu(In,Ga)Se 2 devices for thin absorbers is described. The backwall structure of glass/ITO/MoO 3 /Cu(In,Ga)Se 2 /CdS/i-ZnO/Ag utilizes a MoO 3 transparent back contact to allow illumination of the device from the back. The device performance has been improved by modifying the Cu(In,Ga)Se 2 , including alloying with Ag to form (AgCu)(InGa)Se 2 absorber layers. In addition, sulfized back contacts including ITO-S and MoS 2 are compared. Interface properties are discussed based on the XPS analysis and thermodynamics of reactions.

Kihwan Kim - One of the best experts on this subject based on the ideXlab platform.

  • improved performance of ultrathin cu inga se _ bf 2 solar cells with a backwall Superstrate Configuration
    IEEE Journal of Photovoltaics, 2014
    Co-Authors: Hamed Simchi, Jes K Larsen, Kihwan Kim, William N. Shafarman
    Abstract:

    A backwall Superstrate device structure that outperforms conventional substrate Cu(In,Ga)Se 2 devices for thin absorbers is described. The backwall structure of glass/ITO/MoO 3 /Cu(In,Ga)Se 2 /CdS/i-ZnO/Ag utilizes a MoO 3 transparent back contact to allow illumination of the device from the back. The device performance has been improved by modifying the Cu(In,Ga)Se 2 , including alloying with Ag to form (AgCu)(InGa)Se 2 absorber layers. In addition, sulfized back contacts including ITO-S and MoS 2 are compared. Interface properties are discussed based on the XPS analysis and thermodynamics of reactions.

  • Backwall Superstrate Configuration for ultrathin Cu(In,Ga)Se2 solar cells
    Applied Physics Letters, 2014
    Co-Authors: Jes K Larsen, Hamed Simchi, Peipei Xin, Kihwan Kim, William N. Shafarman
    Abstract:

    A backwall Superstrate device structure that outperforms conventional substrate Cu(In,Ga)Se2 devices for thin absorbers is demonstrated. The backwall structure (glass/In2O3-SnO2/MoO3-x/Cu(In,Ga)Se2/CdS/i-ZnO/Ag) utilizes a MoO3−x transparent back contact to allow illumination of the device from the back. In combination with a silver front reflector this cell structure is tailored to enhance performance of devices with submicron thick absorbers. It was found that devices with the backwall Configuration outperform substrate devices in the absorber thickness range dCIGS = 0.1-0.5 μm. The advantage of the backwall Configuration is mainly through superior JSC, achieved by application of a front reflector and elimination of parasitic absorption in CdS.

  • Improved Performance of Ultrathin Cu(InGa)Se $_{\bf 2}$ Solar Cells With a Backwall Superstrate Configuration
    IEEE Journal of Photovoltaics, 2014
    Co-Authors: Hamed Simchi, Jes K Larsen, Kihwan Kim, William N. Shafarman
    Abstract:

    A backwall Superstrate device structure that outperforms conventional substrate Cu(In,Ga)Se 2 devices for thin absorbers is described. The backwall structure of glass/ITO/MoO 3 /Cu(In,Ga)Se 2 /CdS/i-ZnO/Ag utilizes a MoO 3 transparent back contact to allow illumination of the device from the back. The device performance has been improved by modifying the Cu(In,Ga)Se 2 , including alloying with Ag to form (AgCu)(InGa)Se 2 absorber layers. In addition, sulfized back contacts including ITO-S and MoS 2 are compared. Interface properties are discussed based on the XPS analysis and thermodynamics of reactions.

E. S. R. Gopal - One of the best experts on this subject based on the ideXlab platform.

  • Fabrication of Photovoltaic Devices Using ZnO Nanostructures and SnS Thin Films
    NANO, 2016
    Co-Authors: N. Koteeswara Reddy, M. Devika, K. R. Gunasekhar, E. S. R. Gopal
    Abstract:

    The development of nontoxic and cost-effective solar cell devices is one of the challenging tasks even now. With this objective, solar cell devices using tin mono sulfide (SnS) thin films and zinc oxide (ZnO) nanostructures with a Superstrate Configuration of ITO/ZnO film/ZnO nanorods/SnS film/Zn have been fabricated and their photovoltaic properties have been investigated. Vertically aligned ZnO nanostructures were grown on indium doped tin oxide substrate by chemical solution method and then, SnS thin films were deposited by thermal evaporation method. A typical solar cell device exhibited significant light conversion efficiency with an open circuit voltage and short circuit current of 350mV and 5.14 mA, respectively.

  • Fabrication of Photovoltaic Devices Using ZnO Nanostructures and SnS Thin Films
    Nano, 2016
    Co-Authors: N. Koteeswara Reddy, M. Devika, K. R. Gunasekhar, E. S. R. Gopal
    Abstract:

    The development of nontoxic and cost-effective solar cell devices is one of the challenging tasks even now. With this objective, solar cell devices using tin mono sulfide (SnS) thin films and zinc oxide (ZnO) nanostructures with a Superstrate Configuration of ITO/ZnO film/ZnO nanorods/SnS film/Zn have been fabricated and their photovoltaic properties have been investigated. Vertically aligned ZnO nanostructures were grown on indium doped tin oxide substrate by chemical solution method and then, SnS thin films were deposited by thermal evaporation method. A typical solar cell device exhibited significant light conversion efficiency with an open circuit voltage and short circuit current of 350[Formula: see text]mV and 5.14[Formula: see text]mA, respectively.