Preparation of PEDOT by Solid-State Polymerization Method and Its Application in UV Photodetctor

Poly(3,4-ethylenedioxythiophene) (PEDOT) is used in organic-inorganic heterojunction based ultraviolet (UV) photodetector due to its good environmental stability, high conductivity and special photoelectric characteristics. The commonly used methods for depositing PEDOT films include solution spin coating, electrochemical polymerization, vacuum evaporation and immersion. In this paper, PEDOT film on the surface of fluorine doped tin oxide (FTO) coated glass conductive glass is obtained by solid-state polymerization, using 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT) as monomer. The PEDOT film modified FTO was combined with zinc oxide nano arrays (ZnO NRs) modified FTO to fabricate the organic-inorganic heterojunction based UV photodetector, and the performance of UV photodetection ability was studied. The materials were characterized by ultraviolet-visible spectroscopy (UV-Vis), Fourier-transfer infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and X-ray powder diffractometry (XRD). The photo-responsivity, response speed and stability of the UV photodetector were examined in detail through current-voltag (I-V), current-time (I-t) and Tafel curves at zero bias voltage under UV irradiation (365 nm, 0.32 mW/cm²). Results showed that the PEDOT film had a large flake structure, which was conducive to the good contact of ZnO NRs to build a better p-n heterojunction. Furthermore, the introduction of PEDOT film effectively solved the problems of short carrier life, high recombination rate of hole-electrons and slow light response speed of ZnO NRs. In a word, the PEDOT film enhanced the optoelectronic performance of ZnO NRs, which possessed high responsivity of 15.34 mA/W, fast response time of 0.159 s/0.162 s (rise time/fall time) under UV irradiation (365 nm, 0.32 mW/cm²) and good stability.