Enhanced performance of PFO-ZnO nanorods nanocomposite photodiodes grown on ZnO NRs/ZnO/ITO-coated glass

Abstract

An improved photodiode was fabricated using a nanocomposite of poly (9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) and zinc oxide nanorods (ZnO NRs). The nanocomposite was prepared by scratching hydrothermally grown ZnO NRs on a glass substrate into the prepared PFO solution. The nanocomposite layer was deposited using the spin-coating method and silver (Ag) paste was applied as the electrode. The resulting photodiode configuration is Ag/PEDOT:PSS/PFO-ZnO NR/ZnO NRs/ZnO/ITO. Ultraviolet–visible (UV–Vis) spectroscopy showed a slight blue shift and a slight increase in the optical bandgap. The nanocomposite-based photodiode showed improved performance, due to increased active surface area for the separation of photogenerated electron-hole pairs between PFO and ZnO and also because of the higher current density of ZnO. Finite-Difference Time-Domain (FDTD) simulations showed ZnO NRs increased electric field strength and exciton generation rate throughout the PFO polymer in the nanocomposite. The photodiode with the nanocomposite showed the best performance at −5 V bias voltage under 385 nm illumination, obtaining responsivity of 1.45 A W−1, Detectivity of 2.19 x 1010 Jones, and External quantum efficiency (EQE %) of 468 %.