Optical management in high-efficiency thin-film silicon micromorph solar cells with a silicon oxide based intermediate reflector

Abstract

In the effort to increase the stable efficiency of thin film silicon micromorph solar cells, a silicon oxide based intermediate reflector (SOIR) layer is deposited in situ between the component cells of the tandem device. The effectiveness of the SOIR layer in increasing the photo-carrier generation in the a-Si:H top absorber is compared for p-i-n devices deposited on different rough, highly transparent, front ZnO layers. High haze and low doping level for the front ZnO strongly enhance the current density (Jsc) in the μc-Si: H bottom cell whereas Jsc in the top cell is influenced by the angular distribution of the transmitted light and by the reflectivity of the SOIR related to different surface roughness. A total Jsc of 26.8 mA/cm2 and an initial conversion efficiency of 12.6% are achieved for 1.2 cm2 cells with top and bottom cell thicknesses of 300 nm and 3 μm, and without any anti-reflective coating on the glass. © 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.