Why CuInGaSe2 and CdTe polycrystalline thin film solar cells are more efficient than the corresponding single crystal?

Recently, very high conversion efficiencies in thin film polycrystalline solar cells have been reported. In particular it was reached an efficiency record both for CuInGaSe2 (CIGS) and CdTe that are 19.2% and 16.5% respectively. We will briefly describe the technological methods used to fabricate these thin film solar cells. Besides, we will try to explain the reason why thin film polycrystalline devices can achieve conversion efficiency comparable with those shown by single crystal solar cells (mono-Si or poly-Si). We will take into consideration the tricks present in both the methods that allow to make the CIGS/CdS and CdTe/CdS thin film solar cells with excellent performances. We will show also, that these technologies are ripe for an "inline" industrial production and this makes thin film solar cells the best candidates for the large scale utilisation of photovoltaic energy conversion. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim