Investigations on accelerated processes for the boron–oxygen defect in p-type Czochralski silicon

Abstract

As new solar cell architectures are developed with superior surface passivation, the boron–oxygen defect becomes an increasingly significant limitation on device performance for p-type Czochralski silicon solar cells. This has led to research into methods of permanently deactivating the recombination activity associated with the defect and how these might be implemented in an industrial environment. While the ability to passivate this defect at temperatures below 500K has been widely reported in the literature, recent results from the authors have demonstrated the ability to achieve near complete passivation of this defect at temperatures in excess of 600K under high intensity illumination. This ability to passivate the defect at higher temperatures than previously reported may be explained by an increase in the rate of defect passivation, or alternately, by an increase in the defect formation rate. This paper explores the dependence of defect passivation upon illumination intensity, temperature and the initial state of the defects. Evidence is presented to suggest that high intensity illumination does not significantly increase the rate of passivation, but rather greatly enhances the defect formation rate. Based upon this understanding it is demonstrated how a 10s process under high intensity illumination may be used to completely eliminate the impact of the boron–oxygen defect on solar cell performance, with no requirement for prior defect formation.