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

Abstract As a typical transition metal oxide with high work function, vanadium oxide (V 2 O 5 ) 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 tunneling and trap-assisted tunneling (TAT), which strongly depend on the concentration of oxygen vacancies ( V O ); however, very little work has focused on its effective modulation. Herein, solution-processed V 2 O 5 films are doped with Mo 6+ 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 photoelectric conversion efficiency (PCE) of V 2 O 5 /p-Si heterojunction solar cells being increased from 16.2% to 17.7%, due to the increase of V O induced by the electron transfer from Mo 6+ to V 5+ . The utilization of forming gas annealing further improves the PCE up to 18.2%, ascribed to the generation of more V O and the additional passivation of hydrogen, which is the highest achieved with solution-processed V 2 O 5− X for c-Si heterojunction solar cells up to now.