Reduction of grain boundary recombination in polycrystalline silicon solar cells

Abstract

The possibility of increasing the carrier collection efficiency in polycrystalline silicon by means of a heavily doped region near the grain boundaries is investigated. Phosphorous dopant is preferentially introduced into the grain boundaries of p-type material by a low-temperature diffusion process. A subsequent high-temperature diffusion forms a highly n-doped skin covering each grain. The resulting junction around each grain surface collects electrons which might otherwise recombine at the grain boundaries. This grain boundary doping scheme makes possible an increase in the conversion efficiency of polycrystalline silicon solar cells in which the grain structure is columnar.