Carrier Selectivity and Passivation at the Group V elemental 2D Material--Si Interface of a PV Device

This study investigates the interfacial characteristics relevant to photovoltaic (PV) devices of the Group--V elemental 2D layers with Si. The surface passivation and carrier selectivity of the interface between $\alpha$ and $\beta$ allotropes of arsenene, antimonene, and bismuthene monolayers with Si (100) and Si(111) were estimated \emph{via} first--principles calculations. Amongst the various interface configurations studied, all of the Si(111)--based slabs and only a couple of the Si(100)--based slabs are found to be stable. Bader charge analysis reveals that charge transfer from/to the Si slab to (As)/from (Sb and Bi) in the 2D layer occurs, indicating a strong interaction between atoms across the interface. Comparing within the various configurations of a particular charge (electron or hole) selective layer, the structural distortion of the Si slab is the lowest for $\alpha$--As/Si and $\beta$-Bi/Si. This translates as a lower surface density of states (DOS) in the band gap arising out of the Si slab when integrated with $\alpha$--arsenene and $\beta$--bismuthene, implying better surface passivation. All-in-all, our analysis suggests $\alpha$-As as the best candidate for a passivating electron selective layer, while $\beta$-Bi can be a promising candidate for a passivating hole selective layer.