Modeling the effects of defect parameters on the performance of a p-BaSi2/n-Si heterojunction solar cell

Abstract

Barium disilicide (BaSi2) in thin-film solar cell applications has drawn considerable interest owing to its promising optical and electrical properties. We have achieved an efficiency of 9.9% in p-BaSi2/n-Si heterojunction solar cells, which is the highest performance reported among semiconducting silicide devices; however, this value remains much lower than the theoretical limit as defined by the material's band gap. In this paper, we performed numerical simulations based on Silvaco ATLAS to investigate the effects of defect parameters on the performance of heterojunction solar cells. The defects were modeled by introducing two tail bands around the edge of the conduction and valence bands, and an acceptor-like Gaussian distributed localized energy level within the band gap of BaSi2. The influence of the band tail density of states and the parameters of the localized energy levels on the short-circuit current density, open-circuit voltage, fill factor, and efficiency were evaluated. These results enabled us to reproduce the measured J-V characteristics by simulation.We propose a defect model of p-BaSi2 films to reproduce experimentally obtained current-voltage characteristics of p-BaSi2/n-Si heterojunction solar cell under AM1.5 illumination. Two band tails and one acceptor-like localized energy level reproduce the experimental result.