Superior performance of V2O5 as hole selective contact over other transition metal oxides in silicon heterojunction solar cells

Abstract

Transition metal oxides (TMOs) have recently been proved to efficiently serve as hole-selective contacts in crystalline silicon (c-Si) heterojunction solar cells. In the present work, two TMO/c-Si heterojunctions are explored using MoO3 (reference) and V2O5 as an alternative candidate. It has been found that V2O5 devices present larger (16% improvement) power conversion efficiency mainly due to their higher open-circuit voltage. While V2O5/c-Si devices with textured front surfaces exhibit larger short-circuit currents, it is also observed that flat solar cell architectures allow for passivation of the V2O5/n-Si interface, giving significant carrier lifetimes of 200 μs (equivalent to a surface recombination velocity of Seff ~140cms−1) as derived from impedance analysis. As a consequence, a significant open-circuit voltage of 662mV is achieved. It is found that, at the TMO/c-Si contact, a TMO work function enhancement ΔΦTMO occurs during the heterojunction formation with the consequent dipole layer enlargement Δ’=Δ+ΔΦTMO. Our results provide new insights into the TMO/c-Si contact energetics, carrier transport across the interface and surface recombination allowing for further understanding of the nature of TMO/c-Si heterojunctions.