On the interplay of interface morphology and microstructure of high-efficiency microcrystalline silicon solar cells

Abstract

The relationship between light trapping and microstructure of high-efficiency microcrystalline silicon thin-film solar cells on honeycomb textured substrates is investigated by experiments, optical simulations and analytical calculations. The solar cells realized on the honeycomb textured substrates exhibit short circuit current of 30mA/cm2 and energy conversion efficiencies exceeding 11%. The microstructure of the solar cells is limited by the formation of so called “cracks” in the film, which negatively affect the short circuit current, fill factor and open circuit voltage. The formation of cracks is studied by transmission electron microscopy, optoelectrical measurements and simulations of the 3D morphology of the solar cell. Furthermore, a simple analytical model is presented to calculate the critical thickness at which cracks are formed. Both models are compared to experimental results. Guidelines are provided on how to avoid the formation of cracks in microcrystalline silicon films on the textured substrates while maximizing the light trapping properties.