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A N Tiwari - One of the best experts on this subject based on the ideXlab platform.
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3 dimensional microstructural characterization of cdte absorber layers from cdte cds thin film solar cells
Solar Energy Materials and Solar Cells, 2016Co-Authors: Guillaume Stechmann, Stephan Buecheler, Lukas Kranz, Christina Gretener, Julian Perrenoud, Stefan Zaefferer, Peter Joachim Konijnenberg, Dierk Raabe, A N TiwariAbstract:The present work reports on a study on the microstructure and its evolution during processing of CdTe absorber layers from CdTe/CdS thin film solar cells grown by low-temperature processes in Substrate Configuration. Investigations were performed at different stages of the cell manufacturing, from deposition to the final functional solar cell, with the aim to understand the microstructure formation of the photoactive layer. To this end 3-dimensional microstructure characterization was performed using focused ion beam/electron backscatter diffraction tomography ("3D-EBSD") together with conventional 2D-EBSD. The analyses revealed strong microstructural and textural changes developing across the thickness of the absorber material, between the back contact and the p–n junction interfaces. Based on the 3-dimensional reconstruction of the CdTe thin film, a coherent growth model was proposed, emphasizing the microstructural continuity before and after a typical CdCl2-annealing activation treatment. One of the principal results is that the absorber layer is created by two concomitant processes, deposition and recrystallization, which led to different textures and microstructures. Further changes are the result of subsequent annealing treatments, favoring twinning and promoting well-defined texture components. The results open the possibility for a grain boundary engineering approach applied to the design of such cells.
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cdte thin films doped by cu and ag a comparison in Substrate Configuration solar cells
Photovoltaic Specialists Conference, 2014Co-Authors: Christina Gretener, Stephan Buecheler, Lukas Kranz, Julian Perrenoud, Michael Wyss, A N TiwariAbstract:One of the main problems to be solved in order to raise the efficiency of CdTe solar cells is the low acceptor concentration in polycrystalline CdTe layers which is limiting the open circuit voltage. The commonly used acceptor dopant Cu not only forms rather deep acceptor defects but is also likely to limit the net acceptor concentration due to the formation of compensating donor type defects. In this work, Ag is examined as a possible candidate for improving acceptor concentration in CdTe thin films. Hole density in CdTe layers with varying elemental Ag concentration follows a similar trend as previously reported for Cu doping. In finished solar cells efficiencies up to 11.6 % could be reached using Ag as acceptor dopant. Measurements of hole density, barrier height, space charge region width and depth dependent elemental distribution indicate the similarity of the Ag and Cu doping process.
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cdte cds thin film solar cells grown in Substrate Configuration
Progress in Photovoltaics, 2013Co-Authors: Christina Gretener, Stephan Buecheler, Lukas Kranz, Rafael Schmitt, Julian Perrenoud, Luisa Kneer, A N TiwariAbstract:The ability to grow efficient CdTe/CdS solar cells in Substrate Configuration would not only allow for the use of non-transparent and flexible Substrates but also enable a better control of junction formation. Yet, the problems of barrier formation at the back contact as well as the formation of a p–n junction with reduced recombination losses have to be solved. In this work, CdTe/CdS solar cells in Substrate Configuration were developed, and the results on different combinations of back contact materials are presented. The Cu content in the electrical back contact was found to be a crucial parameter for the optimal CdCl2-treatment procedure. For Cu-free cells, two activation treatments were applied, whereas Cu-containing cells were only treated once after the CdTe deposition. A recrystallization behavior of the CdTe layer upon its activation similar to superstrate Configuration was found; however, no CdTe–CdS intermixing could be observed when the layers were treated consecutively. Remarkably high VOC and fill factor of 768 mV and 68.6%, respectively, were achieved using a combination of MoO3, Te, and Cu as back contact buffer layer resulting in 11.3% conversion efficiency. With a Cu-free MoO3/Te buffer material, a VOC of 733 mV, a fill factor of 62.3%, and an efficiency of 10.0% were obtained. Copyright © 2012 John Wiley & Sons, Ltd.
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progress towards 14 efficient cdte solar cells in Substrate Configuration
Photovoltaic Specialists Conference, 2013Co-Authors: Lukas Kranz, Stephan Buecheler, Rafael Schmitt, Christina Gretener, Julian Perrenoud, Fabian Pianezzi, Alexander R Uhl, Debora Keller, A N TiwariAbstract:CdTe solar cells are conventionally grown in superstrate Configuration. However, the growth in Substrate Configuration offers more control of junction properties as recrystallization of CdTe and junction formation with CdS can be decoupled. In this paper the influence of various annealing treatment conditions of the CdS layer on its morphology and phase and on the device properties is presented. The presence of CdCl2 during this annealing treatment is important for the phase change of the CdS layer to hexagonal wurtzite and for high efficiencies. A CdCl2 treatment of the CdS at 360 °C improves the efficiency of the device without the adverse effect of pinhole formation in the CdS. CdTe solar cells in Substrate Configuration with more than 13% efficiency are achieved as a progress towards 14% efficiency.
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development of moox thin films as back contact buffer for cdte solar cells in Substrate Configuration
Thin Solid Films, 2013Co-Authors: Christina Gretener, Stephan Buecheler, Lukas Kranz, Julian Perrenoud, C Baechler, Songhak Yoon, Yaroslav E Romanyuk, A N TiwariAbstract:Abstract Molybdenum oxide compounds exhibit unique electrical and optical properties depending on oxygen vacancy concentration and composition and therefore, have recently attracted a lot of attention as a hole transport layer in various devices. In this work CdTe solar cells in Substrate Configuration were grown with evaporated MoOx back contact buffer layers and efficiencies of up to 10% could be achieved without using Cu in the back contact processing. The buffer layer – at the CdTe/back contact interface – in the finished cell was found to consist of MoO2 phase instead of the expected MoO3 phase as observed in as-deposited or annealed MoOx layers without CdTe deposition. In order to obtain MoOx buffer layers with desired stoichiometry, MoOx thin films were deposited by radio-frequency sputtering under different growth conditions. The chemical phase, composition, microstructure and optical properties of such layers were studied for their possible use in CdTe solar cells.
Koji Matsubara - One of the best experts on this subject based on the ideXlab platform.
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stabilized 14 0 efficient triple junction thin film silicon solar cell
Applied Physics Letters, 2016Co-Authors: Hitoshi Sai, Takuya Matsui, Koji MatsubaraAbstract:We report on a high-efficiency triple-junction thin-film silicon solar cell fabricated using the Substrate Configuration. An undoped hydrogenated amorphous silicon (a-Si:H) solar cell grown using triode plasma-enhanced chemical vapor deposition, which is more stable against light soaking, was applied to the a-Si:H/μc-Si:H/μc-Si:H triple-junction cells with honeycomb-textured Substrates. To find the best balance in short circuit density and fill factor, we quantitatively investigated the effect of current mismatch on triple-junction cells. Accordingly, a stabilized efficiency of 14.04% was achieved in an a-Si:H/μc-Si:H/μc-Si:H triple-junction solar cell with a minimum light-induced degradation of 4%, setting a new record in this type of solar cells.
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triple junction thin film silicon solar cell fabricated on periodically textured Substrate with a stabilized efficiency of 13 6
Applied Physics Letters, 2015Co-Authors: Takuya Matsui, Takashi Koida, Koji Matsubara, Michio Kondo, Shuichiro Sugiyama, Hirotaka Katayama, Yoshiaki Takeuchi, Isao YoshidaAbstract:We report a high-efficiency triple-junction thin-film silicon solar cell fabricated with the so-called Substrate Configuration. It was verified whether the design criteria for developing single-junction microcrystalline silicon (μc-Si:H) solar cells are applicable to multijunction solar cells. Furthermore, a notably high short-circuit current density of 32.9 mA/cm2 was achieved in a single-junction μc-Si:H cell fabricated on a periodically textured Substrate with a high-mobility front transparent contacting layer. These technologies were also combined into a-Si:H/μc-Si:H/μc-Si:H triple-junction cells, and a world record stabilized efficiency of 13.6% was achieved.
Christina Gretener - One of the best experts on this subject based on the ideXlab platform.
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3 dimensional microstructural characterization of cdte absorber layers from cdte cds thin film solar cells
Solar Energy Materials and Solar Cells, 2016Co-Authors: Guillaume Stechmann, Stephan Buecheler, Lukas Kranz, Christina Gretener, Julian Perrenoud, Stefan Zaefferer, Peter Joachim Konijnenberg, Dierk Raabe, A N TiwariAbstract:The present work reports on a study on the microstructure and its evolution during processing of CdTe absorber layers from CdTe/CdS thin film solar cells grown by low-temperature processes in Substrate Configuration. Investigations were performed at different stages of the cell manufacturing, from deposition to the final functional solar cell, with the aim to understand the microstructure formation of the photoactive layer. To this end 3-dimensional microstructure characterization was performed using focused ion beam/electron backscatter diffraction tomography ("3D-EBSD") together with conventional 2D-EBSD. The analyses revealed strong microstructural and textural changes developing across the thickness of the absorber material, between the back contact and the p–n junction interfaces. Based on the 3-dimensional reconstruction of the CdTe thin film, a coherent growth model was proposed, emphasizing the microstructural continuity before and after a typical CdCl2-annealing activation treatment. One of the principal results is that the absorber layer is created by two concomitant processes, deposition and recrystallization, which led to different textures and microstructures. Further changes are the result of subsequent annealing treatments, favoring twinning and promoting well-defined texture components. The results open the possibility for a grain boundary engineering approach applied to the design of such cells.
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cdte thin films doped by cu and ag a comparison in Substrate Configuration solar cells
Photovoltaic Specialists Conference, 2014Co-Authors: Christina Gretener, Stephan Buecheler, Lukas Kranz, Julian Perrenoud, Michael Wyss, A N TiwariAbstract:One of the main problems to be solved in order to raise the efficiency of CdTe solar cells is the low acceptor concentration in polycrystalline CdTe layers which is limiting the open circuit voltage. The commonly used acceptor dopant Cu not only forms rather deep acceptor defects but is also likely to limit the net acceptor concentration due to the formation of compensating donor type defects. In this work, Ag is examined as a possible candidate for improving acceptor concentration in CdTe thin films. Hole density in CdTe layers with varying elemental Ag concentration follows a similar trend as previously reported for Cu doping. In finished solar cells efficiencies up to 11.6 % could be reached using Ag as acceptor dopant. Measurements of hole density, barrier height, space charge region width and depth dependent elemental distribution indicate the similarity of the Ag and Cu doping process.
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cdte cds thin film solar cells grown in Substrate Configuration
Progress in Photovoltaics, 2013Co-Authors: Christina Gretener, Stephan Buecheler, Lukas Kranz, Rafael Schmitt, Julian Perrenoud, Luisa Kneer, A N TiwariAbstract:The ability to grow efficient CdTe/CdS solar cells in Substrate Configuration would not only allow for the use of non-transparent and flexible Substrates but also enable a better control of junction formation. Yet, the problems of barrier formation at the back contact as well as the formation of a p–n junction with reduced recombination losses have to be solved. In this work, CdTe/CdS solar cells in Substrate Configuration were developed, and the results on different combinations of back contact materials are presented. The Cu content in the electrical back contact was found to be a crucial parameter for the optimal CdCl2-treatment procedure. For Cu-free cells, two activation treatments were applied, whereas Cu-containing cells were only treated once after the CdTe deposition. A recrystallization behavior of the CdTe layer upon its activation similar to superstrate Configuration was found; however, no CdTe–CdS intermixing could be observed when the layers were treated consecutively. Remarkably high VOC and fill factor of 768 mV and 68.6%, respectively, were achieved using a combination of MoO3, Te, and Cu as back contact buffer layer resulting in 11.3% conversion efficiency. With a Cu-free MoO3/Te buffer material, a VOC of 733 mV, a fill factor of 62.3%, and an efficiency of 10.0% were obtained. Copyright © 2012 John Wiley & Sons, Ltd.
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progress towards 14 efficient cdte solar cells in Substrate Configuration
Photovoltaic Specialists Conference, 2013Co-Authors: Lukas Kranz, Stephan Buecheler, Rafael Schmitt, Christina Gretener, Julian Perrenoud, Fabian Pianezzi, Alexander R Uhl, Debora Keller, A N TiwariAbstract:CdTe solar cells are conventionally grown in superstrate Configuration. However, the growth in Substrate Configuration offers more control of junction properties as recrystallization of CdTe and junction formation with CdS can be decoupled. In this paper the influence of various annealing treatment conditions of the CdS layer on its morphology and phase and on the device properties is presented. The presence of CdCl2 during this annealing treatment is important for the phase change of the CdS layer to hexagonal wurtzite and for high efficiencies. A CdCl2 treatment of the CdS at 360 °C improves the efficiency of the device without the adverse effect of pinhole formation in the CdS. CdTe solar cells in Substrate Configuration with more than 13% efficiency are achieved as a progress towards 14% efficiency.
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development of moox thin films as back contact buffer for cdte solar cells in Substrate Configuration
Thin Solid Films, 2013Co-Authors: Christina Gretener, Stephan Buecheler, Lukas Kranz, Julian Perrenoud, C Baechler, Songhak Yoon, Yaroslav E Romanyuk, A N TiwariAbstract:Abstract Molybdenum oxide compounds exhibit unique electrical and optical properties depending on oxygen vacancy concentration and composition and therefore, have recently attracted a lot of attention as a hole transport layer in various devices. In this work CdTe solar cells in Substrate Configuration were grown with evaporated MoOx back contact buffer layers and efficiencies of up to 10% could be achieved without using Cu in the back contact processing. The buffer layer – at the CdTe/back contact interface – in the finished cell was found to consist of MoO2 phase instead of the expected MoO3 phase as observed in as-deposited or annealed MoOx layers without CdTe deposition. In order to obtain MoOx buffer layers with desired stoichiometry, MoOx thin films were deposited by radio-frequency sputtering under different growth conditions. The chemical phase, composition, microstructure and optical properties of such layers were studied for their possible use in CdTe solar cells.
Stephan Buecheler - One of the best experts on this subject based on the ideXlab platform.
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High-efficiency inverted semi-transparent planar perovskite solar cells in Substrate Configuration
Nature Energy, 2016Co-Authors: Fan Fu, Thomas paul Weiss, Stefano Pisoni, Enrico Avancini, Thomas Feurer, Stephan Buecheler, Christian Andres, Ayodhya n. TiwariAbstract:Perovskite solar cells grown in Substrate Configuration would open a range of applications, if various challenges could be overcome. Towards that aim, Fu et al. present an architecture allowing inverted semi-transparent planar perovskite solar cells with open-circuit voltage of 1.116 V and 16.1% efficiency.AbstractThe ability to grow perovskite solar cells in Substrate Configuration, where light enters the devices from the film side, allows the use of non-transparent flexible polymer and metal Substrates. Furthermore, this Configuration could facilitate processing directly on Cu(In,Ga)Se_2 solar cells to realize ultrahigh-efficiency polycrystalline all-thin-film tandem devices. However, the inversion of conventional superstrate architecture imposes severe constraints on device processing and limits the electronic quality of the absorber and charge selective contacts. Here we report a device architecture that allows inverted semi-transparent planar perovskite solar cells with a high open-circuit voltage of 1.116 V and substantially improved efficiency of 16.1%. The Substrate Configuration perovskite devices show a temperature coefficient of −0.18% ^°C^−1 and promising thermal and photo-stability. Importantly, the device exhibits a high average transmittance of 80.4% between 800 and 1,200 nm, which allows us to demonstrate polycrystalline all-thin-film tandem devices with efficiencies of 22.1% and 20.9% for Cu(In,Ga)Se_2 and CuInSe_2 bottom cells, respectively.
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3 dimensional microstructural characterization of cdte absorber layers from cdte cds thin film solar cells
Solar Energy Materials and Solar Cells, 2016Co-Authors: Guillaume Stechmann, Stephan Buecheler, Lukas Kranz, Christina Gretener, Julian Perrenoud, Stefan Zaefferer, Peter Joachim Konijnenberg, Dierk Raabe, A N TiwariAbstract:The present work reports on a study on the microstructure and its evolution during processing of CdTe absorber layers from CdTe/CdS thin film solar cells grown by low-temperature processes in Substrate Configuration. Investigations were performed at different stages of the cell manufacturing, from deposition to the final functional solar cell, with the aim to understand the microstructure formation of the photoactive layer. To this end 3-dimensional microstructure characterization was performed using focused ion beam/electron backscatter diffraction tomography ("3D-EBSD") together with conventional 2D-EBSD. The analyses revealed strong microstructural and textural changes developing across the thickness of the absorber material, between the back contact and the p–n junction interfaces. Based on the 3-dimensional reconstruction of the CdTe thin film, a coherent growth model was proposed, emphasizing the microstructural continuity before and after a typical CdCl2-annealing activation treatment. One of the principal results is that the absorber layer is created by two concomitant processes, deposition and recrystallization, which led to different textures and microstructures. Further changes are the result of subsequent annealing treatments, favoring twinning and promoting well-defined texture components. The results open the possibility for a grain boundary engineering approach applied to the design of such cells.
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cdte thin films doped by cu and ag a comparison in Substrate Configuration solar cells
Photovoltaic Specialists Conference, 2014Co-Authors: Christina Gretener, Stephan Buecheler, Lukas Kranz, Julian Perrenoud, Michael Wyss, A N TiwariAbstract:One of the main problems to be solved in order to raise the efficiency of CdTe solar cells is the low acceptor concentration in polycrystalline CdTe layers which is limiting the open circuit voltage. The commonly used acceptor dopant Cu not only forms rather deep acceptor defects but is also likely to limit the net acceptor concentration due to the formation of compensating donor type defects. In this work, Ag is examined as a possible candidate for improving acceptor concentration in CdTe thin films. Hole density in CdTe layers with varying elemental Ag concentration follows a similar trend as previously reported for Cu doping. In finished solar cells efficiencies up to 11.6 % could be reached using Ag as acceptor dopant. Measurements of hole density, barrier height, space charge region width and depth dependent elemental distribution indicate the similarity of the Ag and Cu doping process.
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cdte cds thin film solar cells grown in Substrate Configuration
Progress in Photovoltaics, 2013Co-Authors: Christina Gretener, Stephan Buecheler, Lukas Kranz, Rafael Schmitt, Julian Perrenoud, Luisa Kneer, A N TiwariAbstract:The ability to grow efficient CdTe/CdS solar cells in Substrate Configuration would not only allow for the use of non-transparent and flexible Substrates but also enable a better control of junction formation. Yet, the problems of barrier formation at the back contact as well as the formation of a p–n junction with reduced recombination losses have to be solved. In this work, CdTe/CdS solar cells in Substrate Configuration were developed, and the results on different combinations of back contact materials are presented. The Cu content in the electrical back contact was found to be a crucial parameter for the optimal CdCl2-treatment procedure. For Cu-free cells, two activation treatments were applied, whereas Cu-containing cells were only treated once after the CdTe deposition. A recrystallization behavior of the CdTe layer upon its activation similar to superstrate Configuration was found; however, no CdTe–CdS intermixing could be observed when the layers were treated consecutively. Remarkably high VOC and fill factor of 768 mV and 68.6%, respectively, were achieved using a combination of MoO3, Te, and Cu as back contact buffer layer resulting in 11.3% conversion efficiency. With a Cu-free MoO3/Te buffer material, a VOC of 733 mV, a fill factor of 62.3%, and an efficiency of 10.0% were obtained. Copyright © 2012 John Wiley & Sons, Ltd.
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progress towards 14 efficient cdte solar cells in Substrate Configuration
Photovoltaic Specialists Conference, 2013Co-Authors: Lukas Kranz, Stephan Buecheler, Rafael Schmitt, Christina Gretener, Julian Perrenoud, Fabian Pianezzi, Alexander R Uhl, Debora Keller, A N TiwariAbstract:CdTe solar cells are conventionally grown in superstrate Configuration. However, the growth in Substrate Configuration offers more control of junction properties as recrystallization of CdTe and junction formation with CdS can be decoupled. In this paper the influence of various annealing treatment conditions of the CdS layer on its morphology and phase and on the device properties is presented. The presence of CdCl2 during this annealing treatment is important for the phase change of the CdS layer to hexagonal wurtzite and for high efficiencies. A CdCl2 treatment of the CdS at 360 °C improves the efficiency of the device without the adverse effect of pinhole formation in the CdS. CdTe solar cells in Substrate Configuration with more than 13% efficiency are achieved as a progress towards 14% efficiency.
Lukas Kranz - One of the best experts on this subject based on the ideXlab platform.
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3 dimensional microstructural characterization of cdte absorber layers from cdte cds thin film solar cells
Solar Energy Materials and Solar Cells, 2016Co-Authors: Guillaume Stechmann, Stephan Buecheler, Lukas Kranz, Christina Gretener, Julian Perrenoud, Stefan Zaefferer, Peter Joachim Konijnenberg, Dierk Raabe, A N TiwariAbstract:The present work reports on a study on the microstructure and its evolution during processing of CdTe absorber layers from CdTe/CdS thin film solar cells grown by low-temperature processes in Substrate Configuration. Investigations were performed at different stages of the cell manufacturing, from deposition to the final functional solar cell, with the aim to understand the microstructure formation of the photoactive layer. To this end 3-dimensional microstructure characterization was performed using focused ion beam/electron backscatter diffraction tomography ("3D-EBSD") together with conventional 2D-EBSD. The analyses revealed strong microstructural and textural changes developing across the thickness of the absorber material, between the back contact and the p–n junction interfaces. Based on the 3-dimensional reconstruction of the CdTe thin film, a coherent growth model was proposed, emphasizing the microstructural continuity before and after a typical CdCl2-annealing activation treatment. One of the principal results is that the absorber layer is created by two concomitant processes, deposition and recrystallization, which led to different textures and microstructures. Further changes are the result of subsequent annealing treatments, favoring twinning and promoting well-defined texture components. The results open the possibility for a grain boundary engineering approach applied to the design of such cells.
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cdte thin films doped by cu and ag a comparison in Substrate Configuration solar cells
Photovoltaic Specialists Conference, 2014Co-Authors: Christina Gretener, Stephan Buecheler, Lukas Kranz, Julian Perrenoud, Michael Wyss, A N TiwariAbstract:One of the main problems to be solved in order to raise the efficiency of CdTe solar cells is the low acceptor concentration in polycrystalline CdTe layers which is limiting the open circuit voltage. The commonly used acceptor dopant Cu not only forms rather deep acceptor defects but is also likely to limit the net acceptor concentration due to the formation of compensating donor type defects. In this work, Ag is examined as a possible candidate for improving acceptor concentration in CdTe thin films. Hole density in CdTe layers with varying elemental Ag concentration follows a similar trend as previously reported for Cu doping. In finished solar cells efficiencies up to 11.6 % could be reached using Ag as acceptor dopant. Measurements of hole density, barrier height, space charge region width and depth dependent elemental distribution indicate the similarity of the Ag and Cu doping process.
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cdte cds thin film solar cells grown in Substrate Configuration
Progress in Photovoltaics, 2013Co-Authors: Christina Gretener, Stephan Buecheler, Lukas Kranz, Rafael Schmitt, Julian Perrenoud, Luisa Kneer, A N TiwariAbstract:The ability to grow efficient CdTe/CdS solar cells in Substrate Configuration would not only allow for the use of non-transparent and flexible Substrates but also enable a better control of junction formation. Yet, the problems of barrier formation at the back contact as well as the formation of a p–n junction with reduced recombination losses have to be solved. In this work, CdTe/CdS solar cells in Substrate Configuration were developed, and the results on different combinations of back contact materials are presented. The Cu content in the electrical back contact was found to be a crucial parameter for the optimal CdCl2-treatment procedure. For Cu-free cells, two activation treatments were applied, whereas Cu-containing cells were only treated once after the CdTe deposition. A recrystallization behavior of the CdTe layer upon its activation similar to superstrate Configuration was found; however, no CdTe–CdS intermixing could be observed when the layers were treated consecutively. Remarkably high VOC and fill factor of 768 mV and 68.6%, respectively, were achieved using a combination of MoO3, Te, and Cu as back contact buffer layer resulting in 11.3% conversion efficiency. With a Cu-free MoO3/Te buffer material, a VOC of 733 mV, a fill factor of 62.3%, and an efficiency of 10.0% were obtained. Copyright © 2012 John Wiley & Sons, Ltd.
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progress towards 14 efficient cdte solar cells in Substrate Configuration
Photovoltaic Specialists Conference, 2013Co-Authors: Lukas Kranz, Stephan Buecheler, Rafael Schmitt, Christina Gretener, Julian Perrenoud, Fabian Pianezzi, Alexander R Uhl, Debora Keller, A N TiwariAbstract:CdTe solar cells are conventionally grown in superstrate Configuration. However, the growth in Substrate Configuration offers more control of junction properties as recrystallization of CdTe and junction formation with CdS can be decoupled. In this paper the influence of various annealing treatment conditions of the CdS layer on its morphology and phase and on the device properties is presented. The presence of CdCl2 during this annealing treatment is important for the phase change of the CdS layer to hexagonal wurtzite and for high efficiencies. A CdCl2 treatment of the CdS at 360 °C improves the efficiency of the device without the adverse effect of pinhole formation in the CdS. CdTe solar cells in Substrate Configuration with more than 13% efficiency are achieved as a progress towards 14% efficiency.
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development of moox thin films as back contact buffer for cdte solar cells in Substrate Configuration
Thin Solid Films, 2013Co-Authors: Christina Gretener, Stephan Buecheler, Lukas Kranz, Julian Perrenoud, C Baechler, Songhak Yoon, Yaroslav E Romanyuk, A N TiwariAbstract:Abstract Molybdenum oxide compounds exhibit unique electrical and optical properties depending on oxygen vacancy concentration and composition and therefore, have recently attracted a lot of attention as a hole transport layer in various devices. In this work CdTe solar cells in Substrate Configuration were grown with evaporated MoOx back contact buffer layers and efficiencies of up to 10% could be achieved without using Cu in the back contact processing. The buffer layer – at the CdTe/back contact interface – in the finished cell was found to consist of MoO2 phase instead of the expected MoO3 phase as observed in as-deposited or annealed MoOx layers without CdTe deposition. In order to obtain MoOx buffer layers with desired stoichiometry, MoOx thin films were deposited by radio-frequency sputtering under different growth conditions. The chemical phase, composition, microstructure and optical properties of such layers were studied for their possible use in CdTe solar cells.
