Tuning the properties of a self-powered UV photodetector based on ZnO and poly(3,4-ethylenedioxythiophene): Poly(styrenesulfonate) by hydrogen annealing of ZnO nanorod arrays

Exploring low cost and high performance self-powered UV photodetectors is very important for applications. In the present work, highly ordered and vertically oriented ZnO nanorod arrays on a glass substrate with an Al doped ZnO seed layer were synthesized by a hydrothermal method. It is shown that the point defects and Fermi level of the ZnO NRs can be effectively tuned by hydrogen annealing. The electrical properties of the ZnO/PSS:PEDOT heterojunctions using the hydrogen annealed ZnO nanorod arrays are improved significantly. A minimum ideality factor of 1.2 and a maximum rectification ratio of 255 at ± 2 V are achieved for the heterojunction with ZnO nanorod arrays annealed at 300 °C under hydrogen atmosphere. It is demonstrated that all the UV photodetectors based on the ZnO/PSS:PEDOT heterojunction can be operated at a self-powered mode with a response time < 1 s. The photodetector with the 300 °C hydrogen annealed ZnO nanorod arrays shows the highest photocurrent of 82 nA and the highest photosensitivity of ~ 1000 at zero bias under 365 nm UV light with an intensity of 2.0 mW/cm2. The improvement in photoelectrical properties of the photodetector is ascribed to the reduced point defects in the ZnO nanorod arrays and increased barrier height of the heterojunction, which is effectively tuned by hydrogen annealing.