Crystalline silicon thin-film solar-cells on silicon- nitride ceramic substrates
Photo voltaics-the generation of electricity from sunlight-is a technically challenging but environmentally benign technology to generate electricity with a large economical potential. However, the major hurdle for its widespread usage is its present high cost. Various thin-film solar cell technologies are investigated to bring down the total cost to an economic value. One of them, the crystalline silicon thin-film (CSiTF) solar cell combines the advantages of conventional wafer-based silicon solar cells such as high efficiency and non-toxicity with the benefits of thin-film technologies such as serial interconnection and large area deposition. This paper reports for the first time the preparation of CSiTF solar cells on specially developed Si3N4 ceramic substrates. Three different types of Si3N4 ceramic wafers were single-sided coated with 10 mum of microcrystalline silicon, which was recrystallized by a zone melting step and subsequently thickened to approx. 30 mum. Optical analysis of the layer surface and cross sections was done to determine the crystallographic properties of the silicon layers, as well as mass spectroscopy to measure the concentration of transition metal impurities. A one-side contacted solar cell process was applied on non-conducting Si.;N4 substrates. The best 1 cm(2) cells achieved an efficiency of 8.0 % with an excellent fill factor of 74 % and an open circuit voltage of 554 mV The solar cell characterization was complemented by measurements of dark current-voltage characteristics, spectrally resolved light beam induced current mapping, and external quantum efficiency.