Advanced light management in Micromorph solar cells.pdf

Available online at Energy Procedia 00 (2009) 000–000 Energy Procedia /locate/procedia Advanced light management in Micromorph solar cells L. Castens*, J. Bailat, S. Benagli, J. H?tzel, D. Borello, J. Steinhauser, B. Dehbozorgi, J. Spitznagel, Y. Djeridane, P-A. Madliger, G. Monteduro, M. Marmelo, G. Androutsopoulos E. Vallat-Sauvain, U. Kroll, J. Meier Oerlikon Solar-Lab SA, Rue du Puits-Godet 12A, CH-2000 Neuchatel, Switzerland Abstract In this study recent results of Micromorph thin film silicon tandem cells with n-doped silicon oxide based intermediate reflectors deposited in the KAI-M industrial PECVD reactor are discussed. From the optical analysis of the devices, specific features in the reflection spectrum attributed to the incorporated intermediate reflector can be observed. In particular, the influence of the Transparent Conductive Oxide (TCO) layer roughness on the reflection spectrum of the cells is studied. Compared to commercial SnO2, reflection losses are reduced and photocurrents are increased by using rougher front TCO-layers like LPCVD-ZnO which should lead to potentially higher efficiencies at same silicon absorber thicknesses. Micromorph tandem cells with intermediate reflector on ZnO leads to 10.18 % efficiency after 1000 h of light-soaking, whereas 10.35 % have been achieved on commercial SnO2. ? 2009 Published by Elsevier B.V. Micromorph; Tandem cells; Intermediate reflector layer; LPCVD ZnO 1. Introduction Thin film silicon Micromorph tandem cells, composed of a top amorphous (a-Si:H) p-i-n cell and a bottom microcrystalline silicon p-i-n (μc-Si:H) cell allow reaching higher initial as well as higher stabilized efficiencies than single-junction cells. They preserve the advantages of thin film silicon technology, such as the possibility of large-area deposition and monolithic series connection. The concept of the Micromorph tandem cells improves the conversion over the whole sunlight spectrum by the combination of a “hig