Out-of-plane polarization modulated band alignments in β-In₂X₃/α-In₂X₃ (X = S and Se) vdW heterostructures

Abstract The construction of two-dimensional (2D) van der Waals (vdW) heterostructures is an effective strategy to overcome the intrinsic disadvantages of individual 2D materials. Herein, by employing first-principles calculations, the electronic structures and potential applications in the photovoltaic field of the β -In 2 X 3 / α -In 2 X 3 (X = S and Se) vdW heterostructures have been systematically unraveled. Interestingly, the band alignments of β -In 2 S 3 / α -In 2 S 3 , β -In 2 Se 3 / α -In 2 Se 3 , and β -In 2 Se 3 / α -In 2 S 3 heterostructures can be transformed from type-I to type-II by switching the polarization direction of α -In 2 X 3 layers. It is highlighted that the light-harvesting ability of the β -In 2 X 3 / α -In 2 X 3 vdW heterostructures is significantly higher than the corresponding monolayers in nearly the entire visible light region. Interestingly, type-II β -In 2 S 3 / α -In 2 Se 3 ↓ heterostructure can achieve the power conversion efficiency of 17.9%, where the α -In 2 Se 3 layer acts as a donor and the β -In 2 S 3 layer displays as the acceptor. The present research not only provides an in-depth understanding that the out-of-plane polarization of α -In 2 X 3 monolayers can efficiently modulate the band edge alignment of the β -In 2 X 3 / α -In 2 X 3 vdW heterostructures, but also paves the way for the application of these heterostructures in the field of photovoltaics and optoelectronics.