Flexible Microcrystalline Silicon Solar Cells on Periodically Textured Plastic Substrates

Roll-to-roll processing of thin film solar cells on flexible low cost substrates is an attractive option to lower the production cost of photovoltaic modules. Plastic substrates like PET or PEN are insulating which potentially offers advantages compared to conducting steel foils. However, plastic substrates require lower processing temperatures and novel schemes for efficient light trapping. In this paper we present results of microcrystalline solar cells on periodically textured substrates. Optical characterization of the back reflector revealed the presence of plasmon resonance effects which are mediated by the periodic structure. In TEM investigations we found that the structure is maintained congruently throughout the high index silicon layers. Microcrystalline silicon solar cells on the textured substrates reveal a gain in photocurrent of 27 % compared to flat reference cells. The gain is largely explained by an improved response in the spectral region between 650 and 1000 nm. The best cells on PEN substrates reached efficiencies of 8.2 %.