Enhanced UV-Vis photodetector performance by optimizing interfacial charge transportation in the heterostructure by SnS and SnSe.

Optimizing interfacial charge transfer in type-II heterostructures, is one promising solution to improve efficiency of the solar energy conversion in photodetectors and solar cells. Herein, the SnS/SnSe/ITO and SnSe/SnS/ITO heterostructures are prepared by two-step physical vapor epitaxial growth. X-ray photoelectron spectroscopy confirms the SnS/SnSe heterostructure belongs to type-II band-alignment. The SnS/SnSe based photodetector shows higher photoresponsivity, which is approximately 2, 9, and 14 times larger than that of SnSe/SnS, SnSe, and SnS, respectively. The improvement of SnS/SnSe in photoelectric response mainly comes from high light harvesting and efficient charge transportation than individual SnSe and SnS, which is verified by UV-Vis absorption spectra. Electrochemical impedance spectroscopy, open circuit potentials, and Mott-Schottky characterization results further confirm that the better photodetection performance of SnS/SnSe/ITO than that of SnSe/SnS/ITO heterostructure is from the appropriate energy level cascade facilitating electron transport. These results provide an effective way to further improve the performance of heterostructure-based optoelectronic devices by an appropriate interface design.