Comparison study on the influence of pure PFO and PFO-ZnO nanorods in PFO/n-Si photodiodes

A comparison study was done on poly (9,9-di-n-octylfluorenyl-2,7-diyl) (PFO)/n-silicon (Si) photodiodes, using pure PFO vs. ZnO nanorods (NRs)-PFO nanocomposite. The nanocomposite was synthesized by mixing scratched-hydrothermally grown ZnO NRs into the prepared PFO solution. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) confirmed the presence of ZnO NRs in PFO, proving successful nanocomposite synthesis. The nanocomposite showed a slight blue-shift in photoluminescence (PL) spectra than pure PFO. The nanocomposite-based photodiode showed improved performance, due to the presence of two heterojunctions (PFO/n-Si and PFO/ZnO NRs) acting as the source of photogenerated electron-hole pairs. A higher current density of ZnO also played an important part in the increase in performance. The photodiodes prepared using PFO-ZnO NRs nanocomposite reported the highest sensitivity at 0 V bias voltage (3920%) and highest responsivity at 8 V bias voltage (0.93 A/W). Lastly, a proposed mechanism diagram was drawn to explain the roles of the two heterojunctions in the workings of the photodiode.