Janus transition-metal dichalcogenides heterostructures for highly efficient excitonic solar cells

Abstract

The emergence of two-dimensional semiconductors opens up new avenues for efficient, ultrathin, and high-quality heterojunction solar cells. Herein, based on first-principles calculations, we present the optoelectronic features of a series of experimentally feasible 2D Janus transition metal dichalcogenides monolayers in a configured van der Waals nanostructure. The assembled heterostructures are energetically, dynamically, and mechanically stable, forming type-II band alignment p–n heterojunctions. Thus, the spatial separation of the photo-generated electron–hole pairs is achieved. In the MoXY-WXY (X, Y= S, Se, Te; and X≠Y) vdW heterostructures, the WXY monolayer acts as a good donor material for the acceptor MoXY material. The minimal conduction band offset among constituent monolayers, ideal donor bandgap, and superior optical absorption make Janus TMDCs vdW nanostructures excellent candidates for photovoltaic conversion in 2D excitonic solar cells. On the other hand, the maximum power conversion efficiencies of designed MoSSe-WSSe, MoSTe-WSTe, and MoSeTe-WSeTe bilayer solar cells are calculated to be 17.90%, 21.82%, and 22.99%, respectively. Our findings point out the potential use of here investigated heterostructures in nanophotonics and high-performance excitonic solar cells.