Abstract
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/SnSe2/ITO and SnSe2/SnS/ITO heterostructures are prepared by two-step physical vapor epitaxial growth. X-ray photoelectron spectroscopy confirms the SnS/SnSe2 heterostructure belongs to type-II band-alignment. The SnS/SnSe2 based photodetector shows higher photoresponsivity, which is approximately 2, 9, and 14 times larger than that of SnSe2/SnS, SnSe2, and SnS, respectively. The improvement of SnS/SnSe2 in photoelectric response mainly comes from high light harvesting and efficient charge transportation than individual SnSe2 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/SnSe2/ITO than that of SnSe2/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.
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