Group V Elemental 2D Materials as Promising Passivating and Carrier Selective Layer for Si Photovoltaic Devices

Electron/hole transport and passivation layer in a photovoltaic (PV) device play crucial roles in dictating the overall device efficiency. Understanding the interface physics between such a layer and the PV absorber is the key to designing efficient architecture. Here, we report the interfacial characteristics of a PV device composed of a Group V elemental 2D layer and Si absorber. Two most naturally occurring allotropes (α and β) of arsenene, antimonene, and bismuthene monolayers were chosen to quantify its surface passivation and carrier selectivity using first-principles calculations. Bader charge analysis reveals that charge transfer from/to the Si to (As)/from (Sb and Bi) in the 2D layer occurs, indicating a strong interaction among the atoms across the interface. The structural distortion of the Si slab is found to be the lowest for α-As/Si and β-Bi/Si. This translates into a lower surface density of states (DOS) when integrated with α-arsenene and β-bismuthene, implying better surface passivation. We propose α-As as the best candidate for passivating the electron selective layer, while β-Bi can be a promising candidate for passivating the hole selective layer.