Space-limited domain annealing of CuI thin films for highly responsive ZnO nanorods based ultraviolet photodetectors

Ultraviolet (UV) photodetectors with high responsivity, fast response speed and better stability have attracted much attention. In this work, heterojunctions based on ZnO nanorods (ZnO NRs)/CuI were successfully prepared by combinational chemical hydrothermal and drop-coating methods, which could be employed as self-powered and external powered UV photodetectors. The ZnO NRs were homogeneous covered and coated by CuI layer. The introduction of CuI enhanced the UV emission and weakened the defect emission of ZnO. The space-limited domain annealing was adopted to post-treat the CuI layer, which is useful to prevent the significant loss of iodine in the thin films. The UV photodetector based on ZnO NRs/CuI shows the responsivities of 86.84 mA W−1 at 0 V bias voltage and 4.41 × 104 mA W−1 at −2.5 V bias voltage under 380 nm irradiation. The rise and decay time for the devices are both 110 ms. The incorporation of CuI benefits the separation of photon-generated carriers. The facile, practical and low-cost synthesis makes ZnO NRs/CuI heterojunction a potential candidate for vertical UV-A photodetectors with high responsivity.