Polyoxovanadate-modified SnO₂ electron transport layer for perovskite photodetectors

SnO₂ is widely used in perovskite photodetectors as an electron transport layer material. The matching of the energy levels of SnO₂ and perovskite is important in carrier transport. Polyoxovanadates (POVs), as semiconductor-like molecules, exhibit good redox and excellent optical properties, which can regulate the energy band structure of SnO₂. Here, K₅MnV₁₁O₃₂·10H₂O (MnV₁₁), K₇MnV₁₃O₃₈·18H₂O (MnV₁₃), (NH₄)₈[V₁₉O₄₁(OH)₉]·11H₂O (V₁₉), and K₁₀[V₃₄O₈₂]·20H₂O (V₃₄) were used to modify an SnO₂ colloidal solution. Energy level tests demonstrated that the conduction band potential (E_CB) of MnV₁₃-modified SnO₂ increased from −4.43 to −4.03 eV, which matched more with the energy level of perovskite. This facilitated the extraction and transmission of photogenerated carriers. X-ray diffraction showed that POV-modified SnO₂ exhibited better crystallinity. Scanning electron microscopy revealed that the grain size of perovskite increased to 580 nm after modification using MnV₁₃. The final results showed that the MnV₁₃-modified perovskite photodetector demonstrated the best efficiency. The photocurrent of the photodetector increased from 26 to 80 μA, and its stability was good. After 720 h, the normalized current values of unencapsulated devices on the MnV₁₃@SnO₂ substrate were maintained at more than 70% of the initial values. The study findings show that introducing POVs into photodetectors is a potential strategy for optimizing the performance of photovoltaic devices.