Tunable band alignment and large power conversion efficiency in a two-dimensional InS/ZnInS heterostructure.

Heterostructures can efficiently modulate the bandgap of semiconductors and enhance the separation of photocarriers, thereby enhancing the performance of optoelectronic devices. Herein, we design an InS/ZnInS van der Waals (vdW) heterostructure and investigate its electronic and photovoltaic properties using first principles calculation. Compared to its individual monolayers, the InS/ZnInS heterostructure not only possesses a smaller band gap of 2.21 eV and superior light absorption performance in the visible short-wavelength region (<500 nm) but also forms a type-II band alignment. Moreover, a large power conversion efficiency (PCE) of 10.86% is achieved. The transformation of the band alignment from type-II to type-I or type-II can be forced using an external electric field, and the PCE can be further increased up to 12.19% at a positive of 0.2 V Å. Within a critical biaxial strain of 4%, the type-II band alignment can be maintained, and a high PCE of 20.80% is achieved at a tensile strain () of 4%. Our results may suggest a potential optoelectronic application direction for the InS/ZnInS heterostructure and offer effective means to enhance its optoelectronic device performance.