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27th European Photovoltaic Solar Energy Conference and Exhibition; 2148-2152, Thin-film solar cells in superstrate configuration have very specific requirements for optical and electrical properties of the front contact, like high transmittance and haze as well as a low sheet resistance. Transparent conductive oxides (TCO) have already been proven to be a good choice, but their optical and electrical properties can be improved even after the deposition by various methods. In this contribution the influence of hydrogen plasma post-treatment on the electro-optical properties of LPCVD grown ZnO:B TCO (BZO) and sputtered ZnO:Al TCO (AZO) as well as on the whole solar cell will be analysed. Organic impurities have been found as drawback of LPCVD-deposition process and as a reason of the strong degradation of BZO films in air. It was found that BZO films exhibit a large carbon concentration that results in increased sheet resistance. H2-plasma treatment leads to etching of carbon impurities and thus provides enhancement of conductivity (mostly by boost of carrier mobility). This allows recovering of degraded BZO and fabrication of thinner BZO films (or less doped). Amorphous silicon thin-film solar cells show significant increase of open circuit voltage and efficiency due to better serial resistance value when deposited on H2-treated BZO. Combination of HCl-etching and H2-plasma treatment has been proposed and investigated to improve the morphology, optical and electronic properties of LPCVD-BZO front contact. It has been found that etching enhances surface topography and thus light scattering while H2-plasma treatment decreases the sheet resistance significantly. The related enhance of overall properties of micromorph silicon solar cells is expected.

25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion, 6-10 September 2010, Valencia, Spain; 3032-3035, In this paper the activities of the photovoltaics group at the EWE research centre – NEXT ENERGY is described. The focus of the work lies on thin film silicon solar cells. A baseline process has been implemented allowing the deposition of state-of-the-art micromorph tandem solar cells. This is done with the goal to substantionally increase the efficiency of this kind of cells in the future and to build up the base for new concepts like triple junction solar cells. Detailed simulations were performed to get physical insight into the fundamental mechanisms in the solar cell and to extract further potential of efficiency enhancement. 3-dimensional optical simulations of structures with realistic topography will be presented. First experiments with ps-laser scribing have been performed for TCO and a-Si:H ablation At the end an outlook about the triple junction activities will be given.