Superior Performance Self-Powered Photodetectors Utilizing the Piezo-Phototronic Effect in SnO Nanosheet/ZnO Nanorod Hybrid Heterojunctions

We have demonstrated the piezo-phototronic effect-induced enhancement in photoconductive response in the visible region under self bias conditions utilizing SnO nanosheet/ZnO nanorod-based bulk heterojunction devices. Valence band spectroscopy of SnO nanosheets revealed an improved charge transfer in the bulk heterojunction of PEDO:PSS-coated SnO nanosheets attached to ZnO nanorods. The photoconduction mechanism in the self-biased heterojunction can be ascribed to the visible light-induced charge carrier generation in SnO nanosheets and their subsequent separation to ZnO and PEDOT:PSS sides because of the built-in electric field. To investigate the role of SnO nanosheets embedded in PEDOT:PSS in the bulk heterojunction form, control devices based on the layered structure have also been studied, and their performance has been found to be much inferior. The hybrid heterojunction has been found to respond under an external mechanical stimulus, which is originated by the piezoelectric effect of the c-axis-oriented ZnO nanorods. Upon the application of a weak compressive force (∼2 mN) along the c-axis of ZnO, the photo-current is found to be enhanced by ∼55 times under zero bias and typically follows the periodicity of the applied stress, revealing the modulation of carrier flow under a strained condition.