Annealing temperature effect on the performances of porous ZnO nanosheet-based self-powered UV photodetectors

Porous ZnO nanosheets (ZnO NSs) may play an important role in self-powered UV photodetectors due to their excellent properties, and their porosity feature affects the photoresponse performance greatly. Porous ZnO NSs were prepared by the hydrothermal method followed with a one-step annealing treatment. The effects of the annealing temperature on the microstructure and photoresponse of porous ZnO NSs and n-ZnO NSs/p-PEDOT:PSS self-powered UV photodetectors were investigated. The results show that the pore density and size of ZnO NSs can be tuned by changing the annealing temperature. At an optimum annealing temperature of 450°C, ZnO NSs exhibit greater absorption capacity for the suitable pore density and size. Meanwhile, more crystal defects due to surface contractile properties increase the number of photogenerated carriers. On this basis, the n-ZnO NSs/p-PEDOT:PSS photodetector presents a larger photocurrent and fast photodetection speed without external bias voltage, indicating the self-powered performance. The higher light absorption and large number of electron-hole pairs resulting from dense pores and surface defects in porous ZnO NSs might account for the enhanced performances.