Dopant-free multilayer back contact silicon solar cells employing V2Ox/metal/V2Ox as an emitter

Abstract

In this study, we present novel multilayer back contact (MLBC) solar cells employing V₂O_x (8 nm)/metal/V₂O_x (8 nm) (VMV) multilayers as dopant-free hole-selective contacts deposited using a thermal evaporation process at low temperature. The optimized V₂O_x films have a high work function and reduced O-deficiency in-gap state energy owing to the introduction of a carefully controlled O₂ partial pressure during the evaporation process. The contact resistivities of VMV (12 nm Ag) and VMV (4 nm Au) contacts with n-Si are 1.58 mΩ cm² and 0.04 mΩ cm², respectively, which are less than that of a 16 nm V₂O_x/n-Si contact. Interestingly, VMV (Au)/n-Si MLBC solar cells demonstrate improved charge carrier transport, leading to an induced p–n junction. Moreover, the dominant interfacial charge carrier transport properties of MLBC solar cells with VMV (Ag)/n-Si and VMV (Au)/n-Si contacts correspond with the diffusion–recombination model, whereas, those of MLBC solar cells with V₂O_x/n-Si and VMV (Ca)/n-Si contacts correspond with the multi-tunneling capture emission model at a high-forward-bias voltage. The use of VMV (4 nm Au) as an emitter achieves an efficiency of 19.02% for this type of MLBC solar cell, which is greater than that of V₂O_x/n-Si solar cells (17.58%). This work has important implications for enabling the fabrication of low-performance dopant-free back contact solar cells with high stability using a simple fabrication process.