WS2 and WSSe bilayer with excellent carrier mobility and power conversion efficiency

The WS2/WSSe and WSSe/WS2 bilayers are constructed using single-layer WS2 and WSSe with a lattice mismatch rate of only 1.85 %, and their structural properties, carrier mobility, electrical properties, and photocatalytic performance are performed using density functional theory. The carrier mobility of WS2/WSSe and WSSe/WS2 bilayers is better than that of single-layer WS2. And the conductivity of the WSSe/WS2 bilayer in the Zigzag direction is superior to that in the Armchair direction. The results of band structure using the HSE06 method demonstrate that the most stable WS2/WSSe and WSSe/WS2 bilayers are type-II band alignment. WS2/WSSe and WSSe/WS2 bilayers can undergo redox reactions at pH = 0 and pH = 7 respectively. And they all emerge a builtin electric field to cause photo-generated carriers to recombine between the layers to upgrade the photocatalytic performance of the bilayer, which is a typical S-scheme heterojunction. And the power conversion efficiency (PCE) of the WS2/WSSe and WSSe/WS2 bilayers are 15.5 % and 15.7 % respectively, so the utilization rate of sunlight is relatively high. In general, WS2/WSSe and WSSe/WS2 bilayers are ideal materials in the field of photocatalytic water splitting.

Automated summary

This study constructs WS2/WSSe and WSSe/WS2 bilayers using single-layer WS2 and WSSe with a lattice mismatch rate of 1.85%. The bilayers exhibit better carrier mobility and conductivity than single-layer WS2. The band structure calculations show that WS2/WSSe and WSSe/WS2 bilayers have type-II band alignment. They also exhibit redox reactions and a built-in electric field, leading to enhanced photocatalytic performance with high power conversion efficiency (PCE) of 15.5% and 15.7%, respectively. Overall, WS2/WSSe and WSSe/WS2 bilayers are promising materials for photocatalytic water splitting.