The Experts below are selected from a list of 84 Experts worldwide ranked by ideXlab platform

Robert W. Collins - One of the best experts on this subject based on the ideXlab platform.

  • Correlations Between Mapping Spectroscopic Ellipsometry Results and Solar Cell Performance for Evaluations of Nonuniformity in Thin-Film Silicon Photovoltaics
    IEEE Journal of Photovoltaics, 2013
    Co-Authors: Lila R. Dahal, Nikolas J. Podraza, Sylvain Marsillac, Zhiquan Huang, Dinesh Attygalle, Carl Salupo, Robert W. Collins
    Abstract:

    An understanding of the relationship between materials property and Thin-Film solar cell performance variations over large areas is of interest for evaluating the impact of macroscopic nonuniformities in scale-up from laboratory cells to production modules. In this study, we have spatially correlated the properties of the hydrogenated Silicon (Si:H) i- and p-layers-as mapped over a 13 cm×13 cm substrate area-with device performance parameters from an array of a-Si:H based n-i-p dot cells. To evaluate materials and device nonuniformities, a 16 × 16 array of dot cells has been fabricated over the substrate area, and this same area has been mapped by spectroscopic ellipsometry (SE).Analysis of the SE data over the full area provides maps of i-layer thickness and band gap, p-layer thickness and band gap, and p-layer surface roughness thickness for the n-i-p solar cell structure. The mapped values adjacent to the devices have been correlated with photovoltaic (PV) device performance parameters. When sufficient nonuniformity exists, these correlations enable optimization based on specific values of the fundamental properties. Alternatively, if the optimum set of properties has been identified, the impact of deviations due to macroscopic uniformities can be evaluated.

  • Real time spectroscopic ellipsometry of Ag/ZnO and Al/ZnO interfaces for back-reflectors in thin film Si:H Photovoltaics
    Thin Solid Films, 2011
    Co-Authors: Lila Raj Dahal, Deepak Sainju, Nikolas J. Podraza, Sylvain Marsillac, Robert W. Collins
    Abstract:

    Abstract Real time spectroscopic ellipsometry (RTSE) has been applied to analyze the optical characteristics of Ag/ZnO and Al/ZnO interfaces used in back-reflector (BR) structures for thin film Silicon Photovoltaics. The structures explored here are relevant to the substrate/BR/Si:H(n-i-p) solar cell configuration and consist of opaque Ag or Al films having controllable thicknesses of microscopic surface roughness, followed by a ZnO layer up to ~ 3000 A thick. The thicknesses of the final surface roughness layers on both Ag and Al have been varied by adjusting magnetron sputtering conditions in order to study the effects of metal film roughness on interface formation and interface optical properties. The primary interface loss mechanisms in reflection are found to be dissipation via absorption through localized plasmon modes for Ag/ZnO and through intraband and interband transitions intrinsic to metallic Al for Al/ZnO.

Magda El-shenawee - One of the best experts on this subject based on the ideXlab platform.

  • Optimization of Silver Nanotoroid Arrays for the Absorption Enhancement of Silicon Thin-Film Solar Cells
    Plasmonics, 2015
    Co-Authors: Nathan Burford, Magda El-shenawee
    Abstract:

    The enhancement of absorbed electromagnetic energy of Thin-Film Silicon Photovoltaics due to toroid-shaped plasmonic nanoparticles is computationally investigated. Using Ansys® HFSS, infinite arrays of silver nanotoroids of various sizes are tuned to maximize the photocurrent generation of the photovoltaic. The obtained results show that larger nanotoroid arrays can be tuned to provide enhanced photocurrent generation that is comparable to traditional sphere-shaped nanoparticles. The highly tunable nature of the resonant frequencies of plasmonic nanotoroid geometries is investigated here, which hold potential advantage over nanoparticles in their ability to enhance electromagnetic energy absorption in the longer wavelength regime of the solar spectrum. The obtained results show that larger nanotoroid arrays can be tuned to provide enhanced photocurrent generation comparable to traditional nanoparticles.

Nathan Burford - One of the best experts on this subject based on the ideXlab platform.

  • Optimization of Silver Nanotoroid Arrays for the Absorption Enhancement of Silicon Thin-Film Solar Cells
    Plasmonics, 2015
    Co-Authors: Nathan Burford, Magda El-shenawee
    Abstract:

    The enhancement of absorbed electromagnetic energy of Thin-Film Silicon Photovoltaics due to toroid-shaped plasmonic nanoparticles is computationally investigated. Using Ansys® HFSS, infinite arrays of silver nanotoroids of various sizes are tuned to maximize the photocurrent generation of the photovoltaic. The obtained results show that larger nanotoroid arrays can be tuned to provide enhanced photocurrent generation that is comparable to traditional sphere-shaped nanoparticles. The highly tunable nature of the resonant frequencies of plasmonic nanotoroid geometries is investigated here, which hold potential advantage over nanoparticles in their ability to enhance electromagnetic energy absorption in the longer wavelength regime of the solar spectrum. The obtained results show that larger nanotoroid arrays can be tuned to provide enhanced photocurrent generation comparable to traditional nanoparticles.

Helmut Stiebig - One of the best experts on this subject based on the ideXlab platform.

  • transparent conducting oxide films for thin film Silicon Photovoltaics
    Thin Solid Films, 2007
    Co-Authors: W. Beyer, Jürgen Hüpkes, Helmut Stiebig
    Abstract:

    The requirements for applications of transparent conducting oxide (TCO) films in thin film Silicon solar cells are reviewed with a focus on sputtered Al doped zinc oxide and fluorine doped tin oxide films. TCO films are employed as a front contact and as part of a highly reflective back contact so that the Silicon absorber layer is embedded by TCO films. The optoelectronic properties of TCO layers and their influence on the solar cell performance are discussed. In addition, recent results on the stability of such films in solar cells and solar modules are presented. While zinc and tin oxides have similar optical and electrical properties, the chemistry is quite different. SnO 2 is highly stable against environmental substances as well as acids and bases but rather unstable against hydrogen plasma. ZnO is little affected by H plasma but quite unstable in acids. This latter property bears the advantage that an easy post-deposition texturing is possible by wet chemical etching. For solar cells, damp heat tests for more than 1000 h revealed the high stability of even non-encapsulated solar modules consisting of a ZnO:Al front contact, microcrystalline Silicon cell and ZnO/Ag back reflector.

  • Transparent conducting oxide films for thin film Silicon Photovoltaics
    Thin Solid Films, 2007
    Co-Authors: W. Beyer, Jürgen Hüpkes, Helmut Stiebig
    Abstract:

    The requirements for applications of transparent conducting oxide (TCO) films in thin film Silicon solar cells are reviewed with a focus on sputtered Al doped zinc oxide and fluorine doped tin oxide films. TCO films are employed as a front contact and as part of a highly reflective back contact so that the Silicon absorber layer is embedded by TCO films. The optoelectronic properties of TCO layers and their influence on the solar cell performance are discussed. In addition, recent results on the stability of such films in solar cells and solar modules are presented. While zinc and tin oxides have similar optical and electrical properties, the chemistry is quite different. SnO2is highly stable against environmental substances as well as acids and bases but rather unstable against hydrogen plasma. ZnO is little affected by H plasma but quite unstable in acids. This latter property bears the advantage that an easy post-deposition texturing is possible by wet chemical etching. For solar cells, damp heat tests for more than 1000 h revealed the high stability of even non-encapsulated solar modules consisting of a ZnO:Al front contact, microcrystalline Silicon cell and ZnO/Ag back reflector. © 2007 Elsevier B.V. All rights reserved.

Nikolas J. Podraza - One of the best experts on this subject based on the ideXlab platform.

  • Correlations Between Mapping Spectroscopic Ellipsometry Results and Solar Cell Performance for Evaluations of Nonuniformity in Thin-Film Silicon Photovoltaics
    IEEE Journal of Photovoltaics, 2013
    Co-Authors: Lila R. Dahal, Nikolas J. Podraza, Sylvain Marsillac, Zhiquan Huang, Dinesh Attygalle, Carl Salupo, Robert W. Collins
    Abstract:

    An understanding of the relationship between materials property and Thin-Film solar cell performance variations over large areas is of interest for evaluating the impact of macroscopic nonuniformities in scale-up from laboratory cells to production modules. In this study, we have spatially correlated the properties of the hydrogenated Silicon (Si:H) i- and p-layers-as mapped over a 13 cm×13 cm substrate area-with device performance parameters from an array of a-Si:H based n-i-p dot cells. To evaluate materials and device nonuniformities, a 16 × 16 array of dot cells has been fabricated over the substrate area, and this same area has been mapped by spectroscopic ellipsometry (SE).Analysis of the SE data over the full area provides maps of i-layer thickness and band gap, p-layer thickness and band gap, and p-layer surface roughness thickness for the n-i-p solar cell structure. The mapped values adjacent to the devices have been correlated with photovoltaic (PV) device performance parameters. When sufficient nonuniformity exists, these correlations enable optimization based on specific values of the fundamental properties. Alternatively, if the optimum set of properties has been identified, the impact of deviations due to macroscopic uniformities can be evaluated.

  • Real time spectroscopic ellipsometry of Ag/ZnO and Al/ZnO interfaces for back-reflectors in thin film Si:H Photovoltaics
    Thin Solid Films, 2011
    Co-Authors: Lila Raj Dahal, Deepak Sainju, Nikolas J. Podraza, Sylvain Marsillac, Robert W. Collins
    Abstract:

    Abstract Real time spectroscopic ellipsometry (RTSE) has been applied to analyze the optical characteristics of Ag/ZnO and Al/ZnO interfaces used in back-reflector (BR) structures for thin film Silicon Photovoltaics. The structures explored here are relevant to the substrate/BR/Si:H(n-i-p) solar cell configuration and consist of opaque Ag or Al films having controllable thicknesses of microscopic surface roughness, followed by a ZnO layer up to ~ 3000 A thick. The thicknesses of the final surface roughness layers on both Ag and Al have been varied by adjusting magnetron sputtering conditions in order to study the effects of metal film roughness on interface formation and interface optical properties. The primary interface loss mechanisms in reflection are found to be dissipation via absorption through localized plasmon modes for Ag/ZnO and through intraband and interband transitions intrinsic to metallic Al for Al/ZnO.