Interface engineering on p-CuI/n-ZnO heterojunction for enhancing piezoelectric and piezo-phototronic performance

The enhanced piezoelectric and piezo-phototronic performance of ZnO-based thin film devices has been achieved by interface engineering. The piezoelectric performance of ZnO thin film is significantly boosted due to the formation of CuI/ZnO heterojunction, which effectively reduce the unfavorable piezopotential screening effect induced by free electrons in n-type ZnO. Furthermore, taking the advantage of the piezo-phototronic effect, the mechanically generated piezocharges lowers the barrier height which largely facilitates the charge transport across the CuI/ZnO heterojunction/interface and the performance of as-fabricated device were further enhanced by external strains. The photosensing behaviors of the CuI/ZnO photodetector are systematically investigated under different strain and illumination conditions. Under compressive strain, the optimum performance of flexible CuI/ZnO thin film as UV photodetector is attributed to the formation of pn heterojunction, which further modulated through the piezo-phototronic effect and improves the efficiency of charge separation as a result. Our works demonstrate merits of piezoelectric and piezo-phototronic effects for the design of energy harvesting and optoelectronic nanodevices by engineering piezoelectric/semiconductor materials interface.