Mo-doped vanadium oxide for p-type silicon solar cells with an improved hole selective contact

Abstract

As a typical transition metal oxide (TMO) with high work function, vanadium oxide (V2O5) is a very promising hole selective layer for efficient crystalline silicon (c-Si) solar cells. The holes are extracted or transported via band-to-band (B2B) tunneling and trap-assisted tunneling (TAT), which strongly depend on the concentration of oxygen vacancies (VO), however, very little work has focused on its effective modulation yet. Herein, solution-processed V2O5 films are doped with Mo6+ to tune the hole selectivity for p-Si heterojunction solar cells. With an appropriate doping concentration of 10 mol%, the surface passivation is improved and the contact resistivity decreases simultaneously. The enhanced hole-selective transport with the dominated TAT mechanism contributes to the photoelectrical conversion efficiency (PCE) of V2O5/p-Si heterojunction solar cells increased from 16.2% to 17.7%, due to the increase of VO induced by the electron transfer from Mo6+ to V5+. The annealing in forming gas further improves the PCE up to 18.2%, ascribed to the generation of more VO and the additional passivation of hydrogen, which is the highest achieved with solution-processed V2O5-X for c-Si heterojunction solar cells up to now.