Impact of silicon wafer thickness on photovoltaic performance of crystalline silicon heterojunction solar cells

The impact of Si wafer thickness on the photovoltaic performance of hydrogenated amorphous silicon/crystalline silicon (a-Si:H/c-Si) heterojunction solar cells was examined from the optical and electrical points of view. Optical characterization of c-Si wafers of various thicknesses showed that a realistic light-trapping scheme, i.e., pyramidally textured Si wafers with a dielectric antireflection coating and a back reflector, realizes an efficient quasi-Lambertian light absorption enhancement, even for very thin wafers. This indicates that high photocurrent densities are achievable by using the realistic light-trapping scheme, assuming that the parasitic absorption loss is minimized. The potentials of open-circuit voltage (V-OC) and the fill factor (FF) of thin c-Si cells were investigated using thin c-Si wafers passivated with intrinsic/doped amorphous silicon film stacks. It was experimentally confirmed that the implied V-OC increases steadily with decreasing wafer thickness down to 30 mu m, while the implied FF weakly depends on the thickness. As a result of the trade-off between light absorption and implied V-OC, a high implied efficiency is expected for a wide range of wafer thicknesses. The V-OC increase by thinning the wafer was also experimentally confirmed in an a-Si:H/c-Si heterojunction with a thickness below 60 mu m, resulting in a conversion efficiency of 21.0%. (C) 2018 The Japan Society of Applied Physics