Acid-Treated PEDOT:PSS Polymer and TiO₂ Nanorod Schottky Junction Ultraviolet Photodetectors with Ultrahigh External Quantum Efficiency, Detectivity, and Responsivity

Vertically aligned TiO2 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 TiO2 NRs. For the improvement of device performance, the electrical conductivity of the polymer was increased by adding dimethyl sulfoxide (DMSO) and concentrated H2SO4 acid. The diode parameters, i.e., work function, series resistance, and ideality factor, were studied for all devices. Photoresponse behavior of the TiO2 nanorod/PEDOT:PSS junction was studied upon illumination of white light of intensity 80 mW/cm2. 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 × 1011 Hz1/2/W) at ∼340 nm wavelength under −1 V bias