A two-dimensional GeSe/SnSe heterostructure for high performance thin-film solar cells

Based on the first-principles calculations, we demonstrated that a GeSe/SnSe heterostructure has type-II band alignment and a direct band gap, which can effectively prevent the recombination of photogenerated electron-hole pairs. Moreover, the GeSe/SnSe heterostructure also exhibits strong optical absorption intensity, which can reach the order of 10(5) cm(-1). Our predicted photoelectric conversion efficiency (PCE) for the GeSe/SnSe heterostructure reaches 21.47%. We also found that the hole carrier mobility of the GeSe/SnSe heterostructure along the x direction has been significantly improved to 6.42 x 10(4) cm(2) V-1 s(-1), which is higher than that of black phosphorus (1 x 10(4) cm(2) V-1 s(-1)). By applying a vertical external electric field, we found that the band gap and band offset of the GeSe/SnSe heterojunction can be effectively tuned. The revealed type-II band alignment, strong optical absorption, superior PCE and superior hole carrier mobility of the GeSe/SnSe heterostructure imply that this new proposed material has broad application prospects in solar cells.