Acid-Treated PEDOT:PSS Polymer and TiO 2 Nanorod Schottky Junction Ultraviolet Photodetectors with Ultrahigh External Quantum Efficiency, Detectivity, and Responsivity

Vertically aligned TiO 2 nanorods (NRs) were synthesized on a fluorine-doped tin oxide-deposited glass substrate by the hydrothermal method. A Schottky junction ultraviolet photodetector was fabricated by spin-coating of the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) polymer on TiO 2 NRs. For the improvement of device performance, the electrical conductivity of the polymer was increased by adding dimethyl sulfoxide (DMSO) and concentrated H 2 SO 4 acid. The diode parameters, i.e., work function, series resistance, and ideality factor, were studied for all devices. Photoresponse behavior of the TiO 2 nanorod/PEDOT:PSS junction was studied upon illumination of white light of intensity 80 mW/cm 2 . Our acid-treated sample demonstrated the highest photocurrent value, which is 10 times larger than that of DMSO-treated and 39 times larger than that of the untreated sample. Our acid-treated device showed superior external quantum efficiency (∼12 560%), responsivity (∼34.43 A/W), and detectivity (∼1.6 × 10 11 Hz 1/2 /W) at ∼340 nm wavelength under −1 V bias.