Interlayer coupling prolonged the photogenerated carrier lifetime of few layered Bi2OS2 semiconductors

Abstract

Layered semiconductors with broad photoabsorption, a long carrier lifetime and high carrier mobility are of crucial importance for high-performance optoelectronic and photovoltaic devices; however it is hard to satisfy these requirements simultaneously in a system due to the opposite dependence on the layer thickness. Herein, by means of ab initio time-domain nonadiabatic molecular dynamic simulations, we find a new mechanism in Bi₂OS₂ nanosheets inducing an anomalous layer-dependent property of carrier lifetimes, which makes the few layered Bi₂OS₂ a possible system for fulfilling the above requirements concurrently. It is revealed that the interlayer dipole–dipole interaction in few layered Bi₂OS₂ effectively breaks the two-fold degenerate orbitals of [BiS₂] layers, which not only cuts down the overlap of the electron and hole wave functions, but also accelerates the electron decoherence process. This significantly suppresses the electron–hole recombination and prolongs the photogenerated carrier lifetime of few layered Bi₂OS₂. The mechanism unveiled here paves a possible way for developing advanced optoelectronic and photovoltaic devices through engineering interlayer dipole–dipole coupling.