Thin Film Polycrystalline Silicon Solar Cells Prepared by Plasma CVD

Abstract

The use of RF plasma-assisted chemical vapour deposition (PACVD) for the growth of thin film polycrystalline silicon solar cells on carbon substrates is reported. Efficiencies of upto 5.3% (air mass 1.5, 100 mW/cm 2 irradiation) have been attained in structures employing 10 to 15 μm thick silicon layers deposited at 800 °C, with growth rates upto 10 μm/h. The cells exhibited excellent stabilities under continuous light soaking over a period of 3600 h which was the limit of the test. Fill factor and open circuit voltage were the main factors limiting cell efficiency, the former due to a high series resistance from which all the cells suffered. Short circuit currents were promising at upto 23 mA/cm 2 without the use of AR coatings or light trapping. In view of the non-optimised nature of the cells (e.g. series resistance, doping levels, emitter thicknesses, optical losses, etc.) and the small grain size (≤1 μm) of the layers, the results suggest that further improvements in performance should be possible with optimisation.