Fabrication of p-Cu2O/n-Bi-WO3 heterojunction thin films: optical and photoelectrochemical properties

A transparent n-type Bi-doped WO3 (Bi-WO3) thin film with a thickness of ca. 200 nm was fabricated on fluorine-doped tin oxide (FTO) coated glass using a facile spin-coating and annealing method. The compact WO3 layer with a very smooth surface highly enhanced the transmittance of the FTO substrate. Thin p-type Cu2O films with different morphologies were prepared on the Bi-WO3 film by electro-deposition of the same copper precursor solution with different pH values (7, 9 and 11). Magnetic stirring has a limited effect on the PEC performance of the films in our deposition system. The morphologies of the as-obtained films were characterized by scanning electron microscopy, which shows that the films were uniformly composed of nano-sized particles. The photoelectrochemical properties of the films were comparatively studied. Compared with the Bi-WO3 film, Cu2O/Bi-WO3 fabricated at pH 7 showed a better anodic photocurrent via the formation of a p-n heterojunction.