Beneficial Effects of Dopant Compensation on Carrier Lifetime in Upgraded Metallurgical Silicon

Abstract

This study is devoted to the variations of the carrier lifetime and minority carrier diffusion length with the compensation level in solar-grade crystalline silicon. Especially we show, by using the Shockley-Read-Hall statistics, that an increase in the compensation level reduces the recombination strength of doping species and of some metal impurities. These theoretical results are confirmed by the chemical and electrical characterizations of strongly compensated multicrystalline silicon wafers and solar cells, from silicon purified by the metallurgical route. These results are of paramount importance since an accurate control of the compensation level can lead to strong improvements in silicon solar cells efficiencies. Nevertheless, possible limits of too high compensation levels are also evoked.