TCOs for nip thin film silicon solar cells

Substrate configuration allows for the deposition of thin film silicon (Si) solar cells on non‐transparent substrates such as plastic sheets or metallic foils. In this work, we develop processes compatible with low Tg plastics. The amorphous Si (a‐Si:H) and microcrystalline Si (µc‐Si:H) films are deposited by plasma enhanced chemical vapour deposition, at very high excitation frequencies (VHF‐PECVD). We investigate the optical behaviour of single and triple junction devices prepared with different back and front contacts. The back contact consists either of a 2D periodic grid with moderate slope, or of low pressure CVD (LP‐CVD) ZnO with random pyramids of various sizes. The front contacts are either a 70 nm thick, nominally flat ITO or a rough 2 µm thick LP‐CVD ZnO. We observe that, for a‐Si:H, the cell performance depends critically on the combination of thin flat or thick rough front TCOs and the back contact. Indeed, for a‐Si:H, a thick LP‐CVD ZnO front contact provides more light trapping on the 2D periodic substrate. Then, we investigate the influence of the thick and thin TCOs in conjunction with thick absorbers (µc‐Si:H). Because of the different nature of the optical systems (thick against thin absorber layer), the antireflection effect of ITO becomes more effective and the structure with the flat TCO provides as much light trapping as the rough LP‐CVD ZnO. Finally, the conformality of the layers is investigated and guidelines are given to understand the effectiveness of the light trapping in devices deposited on periodic gratings. Copyright © 2008 John Wiley & Sons, Ltd.

[1]  C. Ballif,et al.  Development of micromorph tandem solar cells on flexible low cost plastic substrates , 2009 .

[2]  C. Ballif,et al.  N/I buffer layer for substrate microcrystalline thin film silicon solar cell , 2008 .

[3]  C. Ballif,et al.  Plasmonic absorption in textured silver back reflectors of thin film solar cells , 2008 .

[4]  M. Topič,et al.  Simulation of losses in thin‐film silicon modules for different configurations and front contacts , 2008 .

[5]  Christophe Ballif,et al.  Optical management in high‐efficiency thin‐film silicon micromorph solar cells with a silicon oxide based intermediate reflector , 2008 .

[6]  V. Terrazzoni-Daudrix,et al.  Optimization of amorphous silicon thin film solar cells for flexible photovoltaics , 2008 .

[7]  Arvind Shah,et al.  Relation between substrate surface morphology and microcrystalline silicon solar cell performance , 2008 .

[8]  J. Owens,et al.  Optical Enhancement by Textured Back Reflector in Amorphous and Nanocrystalline Silicon Based Solar Cells , 2008 .

[9]  C. Ballif,et al.  Optical developments for silicon thin film solar cells in the substrate configuration , 2008 .

[10]  P. Buehlmann,et al.  In situ silicon oxide based intermediate reflector for thin-film silicon micromorph solar cells , 2007 .

[11]  Helmut Stiebig,et al.  Thin-film silicon solar cells with efficient periodic light trapping texture , 2007 .

[12]  Helmut Stiebig,et al.  Optical properties of thin‐film silicon solar cells with grating couplers , 2006 .

[13]  A. Shah,et al.  Characterisation of rough reflecting substrates incorporated into thin‐film silicon solar cells , 2006 .

[14]  B. Rech,et al.  Thin-film silicon solar cells with grating couplers – An experimental and numerical study , 2006 .

[15]  R. Schropp,et al.  Optimization of n–i–p protocrystalline SiGe:H thin film solar cells for application in thin film multijunction solar cells , 2006 .

[16]  D. Domine,et al.  Micromorph Solar Cell Optimization using a ZnO Layer as Intermediate Reflector , 2006, 2006 IEEE 4th World Conference on Photovoltaic Energy Conference.

[17]  A. Shah,et al.  High-Efficiency P-I-N Microcrystalline and Micromorph Thin Film Silicon Solar Cells Deposited on LPCVD Zno Coated Glass Substrates , 2006, 2006 IEEE 4th World Conference on Photovoltaic Energy Conference.

[18]  C. Ballif,et al.  Flexible microcrystalline silicon solar cells on periodically textured plastic substrates , 2006 .

[19]  Reinhard Carius,et al.  Microcrystalline silicon solar cells deposited at high rates , 2005 .

[20]  Arvind Shah,et al.  Low pressure chemical vapour deposition of ZnO layers for thin-film solar cells: temperature-induced morphological changes , 2005 .

[21]  J. Springer,et al.  Effect of Rough ZnO Layers in Improving Performances of Microcrystalline Silicon Solar Cell , 2005 .

[22]  Recent Development of Solar Cells on Low-Cost Plastic Substrates , 2005 .

[23]  J. Springer,et al.  Absorption loss at nanorough silver back reflector of thin-film silicon solar cells , 2004 .

[24]  K. Saito,et al.  High efficiency large area solar cells using microcrystalline silicon , 2003, 3rd World Conference onPhotovoltaic Energy Conversion, 2003. Proceedings of.

[25]  T. Moriarty,et al.  High-efficiency amorphous and "micromorph" silicon solar cells , 2003, 3rd World Conference onPhotovoltaic Energy Conversion, 2003. Proceedings of.

[26]  Marko Topič,et al.  Analysis of light scattering in amorphous Si:H solar cells by a one‐dimensional semi‐coherent optical model , 2003 .

[27]  Arvind Shah,et al.  Microcrystalline Silicon and the Impact on Micromorph Tandem Solar Cells , 2002 .

[28]  Enhanced light-trapping for micromorph tandem solar cells by LP-CVD ZnO , 2002, Conference Record of the Twenty-Ninth IEEE Photovoltaic Specialists Conference, 2002..

[29]  J. Springer,et al.  Improved Optical Model for Thin-film Silicon Solar Cells , 2002 .

[30]  M. Stutzmann,et al.  Periodic light coupler gratings in amorphous thin film solar cells , 2001 .

[31]  T. Sawada,et al.  Large-area and high efficiency a-Si/poly-Si stacked solar cell submodule , 2000, Conference Record of the Twenty-Eighth IEEE Photovoltaic Specialists Conference - 2000 (Cat. No.00CH37036).

[32]  B. Rech,et al.  Texture etched ZnO:Al coated glass substrates for silicon based thin film solar cells , 1999 .

[33]  Kenji Yamamoto,et al.  Thin-film poly-Si solar cells on glass substrate fabricated at low temperature , 1999 .

[34]  R. Morf,et al.  Submicrometer gratings for solar energy applications. , 1995, Applied optics.

[35]  G. Tao,et al.  Computer modelling of a-Si:H based solar cells , 1995 .

[36]  S. Guha,et al.  Study of back reflectors for amorphous silicon alloy solar cell application , 1991 .

[37]  D. Staebler,et al.  Reversible conductivity changes in discharge‐produced amorphous Si , 1977 .

[38]  R. Chittick,et al.  The Preparation and Properties of Amorphous Silicon , 1969 .

[39]  P. Beckmann,et al.  The scattering of electromagnetic waves from rough surfaces , 1963 .