Fabrication and evaluation of figures of merit of ZnO polymer-based hybrid UV photodiodes

This work reports on the fabrication of ZnO polymer-based hybrid ultraviolet (UV) photodiodes with a configuration of ITO/ZnO-nanorod/F8BT/PEDOT:PSS/Ag. The diode was fabricated by spin-coating p-type F8BT and PEDOT:PSS polymers on hydrothermally grown n-type ZnO nanorods. The growth of ZnO nanorods was carried out by varying seed layer alcohols, viz., methanol, ethanol, isopropanol, and aqueous ethanol (70% alcohol). These solvents influenced the nanorod diameter, surface coverage, and surface defects. Herein, we demonstrate that the uniformity and defects in ZnO nanorods govern the electrical properties, photoresponse, and figures of merit of the photodiodes. In particular, the photodiodes are evaluated on their rectification ratio, ideality factor (η), responsivity (R), external quantum efficiency (EQE), and response time (Tdecay). The photodiode fabricated with ZnO nanorods grown on the methanol seeding layer has demonstrated the best performance, owing to the uniform surface coverage of the nanorods. It also presented the highest rectification ratio of ∼640, a Tdecay of 108 s, a η of 2, an EQE of ∼2760%, and an R of ∼8.14 A/W at −2 V.