Survey of Tetragonal Transition Metal Chalcogenide Hetero-Bilayers for Promising Photocatalysts

The formation of van der Waals (vdW) hetero-bilayers have been emerging as unique structures to improve the performance of 2D layered nanomaterials for next-generation photocatalysts. In this work, first-principles calculations are employed to study the electronic and optical properties of a variety of tetragonal transition metal chalcogenide hetero-bilayers. It is found that there are three stable semiconductor/semiconductor vdW hetero-bilayers, and twenty-one stable semiconductor/conductor vdW hetero-bilayers. It is revealed that ZnS/ZnSe and ZnSe/ZnTe hetero-bilayers possess a special band characteristic that is favorable for reducing the carrier recombination. In semiconductor/conductor hetero-bilayers, the band edges of semiconductor are tuned via Schottky barrier, including p-type and n-type Schottky barrier. This work suggests that all hetero-bilayers have an enhanced optical absorption within the visible light region, leading to more efficient solar energy harvesting. Based upon the theoretical calculations, tetragonal transition metal chalcogenide hetero-bilayers will be great candidates as high performance photocatalysts for solar water splitting, as well as many other optoelectronic applications.