Enhanced Broadband Photoresponsivity of the CZTS/WSe2 Heterojunction by Gate Voltage

High-performance photodetectors play critical roles in numerous photon-based applications in imaging, communication, and energy harvesting. Nowadays, heterostructures have received significant attention to extend the performance of photodetectors, with exceptionally high optical absorption and a wide absorption range. However, the enhancement factors, exact mechanism, and facile fabrication procedures are long-standing problems. Here, a heterojunction of a two-dimensional chemical vapor deposition-grown monolayer of WSe2 with a Cu2ZnSnS4 (CZTS) film is introduced. The CZTS film as an abundant material was synthesized in the form of nanoparticles, and it showed a great effect on the enhancement of light absorption. By control of the gate voltage, the results of optoelectronic measurements reveal fast response (2.5 ms) and broadband photoresponsivity (similar to 550 A/W for 395-980 nm), which are about 2500 times higher than those of a conventional WSe2 structure. The energy band structure at the interface of the heterojunction and simulated data with/without a gate voltage were used to investigate the device operation mechanism. It has been realized that the gate voltage has direct impacts on increasing the photocurrent and suppressing the recombination of the photocarriers. The observed experimental results and the proposed mechanism pave shortcuts to developing efficient photodetectors based on transition metal dichalcogenides and earth-abundant materials.