Abstract: In this paper, FTO conductive glass was used as a substrate to successfully prepare Co₃O₄ thin films with controlled morphology by hydrothermal method. Using the prepared Co₃O₄ thin films as the base, Co₃O₄@BiVO₄ composite thin films with varying amounts of BiVO₄ were successfully prepared by controlling the number of spin-coating cycles. The phase composition and microstructure were analyzed using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). Additionally, their optical absorption and photoelectric properties were measured using a UV-3600 UV-Vis spectrophotometer and an electrochemical workstation. Results indicate that, based on the XRD patterns of the Co₃O₄@BiVO₄ composite thin films, the composite materials were successfully prepared. From the FESEM images, it can be observed that the prepared Co₃O₄@BiVO₄ composite thin films possess a continuous, uniform, and dense surface, with the Co₃O₄ thin films growing uniformly as nanowires, and the spin-coated BiVO₄ uniformly coating the surfaces of Co₃O₄ nanowires in a block-like manner. The optical absorption spectrum reveals enhanced light absorption of the Co₃O₄@BiVO₄ composite thin films compared to pure Co₃O₄ thin films. Under zero bias voltage and illumination, the photoelectrical performance of the Co₃O₄@BiVO₄ composite thin films surpasses that of pure Co₃O₄ thin films. Electrochemical test results demonstrate that the Co₃O₄@BiVO₄-3 composite thin films, which were spun-coated three times, showing optimal photoelectrical performance, with a maximum photocurrent approximately 18.4 times that of pure Co₃O₄ thin films. The responsivity of the device is 105.5 μA/W, with a detectivity of up to 1.988×10¹¹ Jones.

Key words: Co₃O₄, BiVO₄, composite film, photoelectric property, photocurrent, detectivity