Switch type PANI/ZnO core-shell microwire heterojunction for UV photodetection

In this study, single crystal ZnO microwires (MW) with size of ∼5.4 mm × 30 μm are prepared through a chemical vapor deposition technique at high temperature (1200 °C). Subsequently, p-type conducting polyaniline (PANI) polymers with different conductivities are densely coated on part of the ZnO MW to construct organic/inorganic core-shell heterojunction photodetectors. The hetero-diodes reach an extremely high rectification ratio (I+3V/I-3V) of 749230, and a maximum rejection ratio (I350nm/Idark) of 3556 (at -3 V), indicating great potential as rectified switches. All the heterojunction devices exhibit strong response to ultraviolet (UV) radiation with high response speed. Moreover, the obvious photovoltaic behavior can also be obtained, allowing the device to operate as an independent and stable unit without externally supplied power. Under 0 V bias voltage, the self-powered photodetector shows a maximum responsivity of 0.56 mA W−1 and a rapid response speed of 0.11 ms/1.45 ms (rise time/decay time). Finally, a finite difference time domain (FDTD) simulation is performed to further demonstrate the interaction mechanism between the incident light field and the hexagonal cavity, which strongly supports the enhancement of the light absorption in whispering-gallery-mode resonator.