Estudo teórico de propriedades eletrônicas e ópticas de heteroestruturas de van der Waals

Abstract

In this work, we examine the energetic, structural, electronic and optical properties of van der Waals heterostructures, based on first-principles calculations. The investigated interfaces were: (i) silicene/WSSe (metal-semiconductor) interface and (ii) MoSe2/WSSe (semiconductor-semiconductor). For cases (i) and (ii), the results indicate that the formation of the interface is driven by an exothermic process, where a charge transfer from silicene (WSSe) to WSSe (MoSe2) occurs, respectively. Furthermore, the results of the electronic properties show that, for cases (i) and (ii), the formation presents type-I and type-II band alignment characteristics, respectively. The optical properties obtained from the solution of the Bethe-Salpeter equation indicate, for case (i), that the power conversion efficiency of the heterostructure is 2.42 times higher than that of the WSSe (Janus) monolayer. On the other hand, for the MoSe2/WSSe heterobilayer, the lowest-energy excitonic states were verified. The results reveal that the first dipole-allowed state has an interlayer character with a transition rate ∼ 616 times lower than that of the intralayer ones. Consequently, this small transition rate implies a longer radiative lifetime of up to three orders of magnitude higher than that of the lowest-energy intralayer exciton. These findings emphasize that the formation of Janus-based heterobilayers presents a considerable improvement in optical properties compared to monolayers, which indicates their potential for application in optoelectronic devices