Optical sensing and nonlinear optical properties of Cr-doped MoO3/PEDOT:PSS Nanocomposites

In this study, we observed a negative UV photoresponse that switched to a positive photoresponse in Cr-doped MoO₃/PEDOT:PSS nanocomposite films(NCF) prepared via drop-casting. MoO₃ and Cr-doped MoO₃ were synthesized using a hot oil bath co-precipitation method, combined with PEDOT:PSS (poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate)), and coated onto flexible OHP sheets. The open aperture z-scan method investigated the nonlinear optical properties of NCF on the glass substrate. The films were characterized by X-ray diffraction, scanning electron microscopic (SEM), UV–Vis spectroscopy, and Fourier Transformed Infrared (FTIR). Chromium doping caused minor changes in lattice parameters, crystalline size, and microstrain. UV spectroscopy revealed an increase in bandgap with higher Cr–MoO₃ concentrations. The photoresponse of different Cr–MoO₃ concentrations showed an initial current decrease under UV light, but the photoresponse became positive beyond a threshold and continued to improve. Nonlinear optical studies indicated saturable absorption in the nanocomposite. This work enhances our understanding of Cr-doped MoO₃/PEDOT:PSS nanocomposites, contributing to advancements in flexible UV photodetectors and nonlinear optical applications.