Effects of Substrate Surface Morphology on Microcrystalline Silicon Solar Cells

The relationship between µc-Si:H solar cell performance and surface morphology of substrate is studied systematically using textured-ZnO substrate which is formed by wet etching process in order to clarify the optimum morphology of substrate for high efficiency. An average slope, tan θ, of substrate surface textures is obtained by analysis of atomic force microscopy (AFM) images, and solar cell performance is correlated with the value os tan θ. As a result, because of the balance between the optical confinement and the grain boundary formation, a conversion efficiency shows a maximum at a tan θ of 0.08 which is 3 times smaller as compared to that used for a-Si:H. An efficiency of 9.4% (Voc=0.526 V, Jsc=25.3 mA/cm2, FF=0.710) is obtained at a deposition temperature of 140°C using the optimized morphology.