ZnO Quantum Dot Decorated Zn2SnO4 Nanowire Heterojunction Photodetectors with Drastic Performance Enhancement and Flexible Ultraviolet Image Sensors

Here we report the fabrication of high-performance ultraviolet photodetectors based on a heterojunction device structure in which ZnO quantum dots were used to decorate Zn2SnO4 nanowires. Systematic investigations have shown their ultrahigh light-to-dark current ratio (up to 6.8 × 104), specific detectivity (up to 9.0 × 1017 Jones), photoconductive gain (up to 1.1 × 107), fast response, and excellent stability. Compared with a pristine Zn2SnO4 nanowire, a quantum dot decorated nanowire demonstrated about 10 times higher photocurrent and responsivity. Device physics modeling showed that their high performance originates from the rational energy band engineering, which allows efficient separation of electron–hole pairs at the interfaces between ZnO quantum dots and a Zn2SnO4 nanowire. As a result of band engineering, holes migrate to ZnO quantum dots, which increases electron concentration and lifetime in the nanowire conduction channel, leading to significantly improved photoresponse. The enhancement mecha...