Polymer-electrolyte-integrated Cr-doped TiO2/Mo-doped BiVO4 heterostructures for quasi-solid-state photovoltaic applications

To overcome the limited visible-light response of pristine titanium dioxide (TiO 2 ) nanorod arrays (TNRAs) and the restricted electron transport of bismuth vanadate (BiVO 4 ) sensitization layers, chromium (Cr)-doped TNRAs coupled with molybdenum (Mo)-doped BiVO 4 (Cr-TNRAs/Mo-BiVO 4 ) were constructed as composite photoanodes and integrated into quasi-solid-state electrolyte (QSE)-based photovoltaic devices. Cr doping was used to regulate the optical absorption and carrier-transport behavior of the TiO 2 nanorod scaffold, while Mo-BiVO 4 served as a visible-light sensitization layer to broaden the spectral response and modulate interfacial charge transfer. The photovoltaic performance of Cr-TNRAs first increased and then decreased with Cr doping level, and Cr-TNRAs-2 showed the best response among the single-doped samples. After Mo-BiVO 4 sensitization, the device output was clearly improved. The optimized Cr-TNRAs-2/Mo-BiVO 4 -2 device achieved a short-circuit current density ( J sc ) of 2.79 mA‧cm −2 , an open-circuit voltage ( V oc ) of 0.44 V and a PCE of 0.38%. UV-vis spectra revealed that the apparent band gap decreased to 2.465-2.481 eV after sensitization, indicating an extended photoresponse. Electrochemical impedance spectroscopy (EIS) results indicated that appropriate Mo-BiVO 4 loading regulates interfacial charge transfer, while device output depends on the combined effects of light absorption, recombination, film quality and charge transport. The optimized device retained about 92% of its photocurrent after 18000 s of intermittent illumination under standard illumination conditions. These results suggest that coupled optimization of the TiO 2 scaffold, BiVO 4 sensitization layer and QSE interface is a feasible route for improving TiO 2 /BiVO 4 -based quasi-solid-state photovoltaic devices.