Microscopic origins of performance losses in highly efficient Cu In, Ga Se2 thin film solar cells

Thin film solar cells based on polycrystalline absorbers have reached very high conversion efficiencies of up to 23 25 . In order to elucidate the limiting factors that need to be overcome for even higher efficiency levels, it is essential to investigate microscopic origins of loss mechanisms in these devices. In the present work, a high efficiency 21 without anti reflection coating copper indium gallium diselenide CIGSe solar cell is characterized by means of a correlative microscopy approach and corroborated by means of photoluminescence spectroscopy. The values obtained by the experimental characterization are used as input parameters for two dimensional device simulations, for which a real microstructure was used. It can be shown that electrostatic potential and lifetime fluctuations exhibit no substantial impact on the device performance. In contrast, nonradiative recombination at random grain boundaries can be identified as a significant loss mechanism for CIGSe solar cells, even for devices at a very high performance leve