Polyoxovanadate-modified SnO ₂ electron transport layer for perovskite photodetectors

As an electron transport layer (ETL) material, SnO₂ is widely used in perovskite photodetectors. The matched energy level alignment between SnO₂ and perovskite is of significance to carrier transport. Polyoxovanadates (POVs), as a semiconductor-like molecule, have good redox properties 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), K₁₀[V₃₄O₈₂]·20H₂O (V₃₄) modified SnO₂ colloidal solution. The energy level test demonstrates that conduction band potential (<em>E_CB</em>) of MnV₁₃ modified SnO₂ is increased from -4.43 eV to -4.03 eV, which is more matched with the energy level of perovskite. It is beneficial to the extraction and transmission of photogenerated carriers. X-ray diffraction (XRD) shows that POVs modified SnO₂ has better crystallinity. Scanning electron microscope (SEM) characterization shows that the grain size of perovskite increases to 580 nm after MnV₁₃ modified. The final results show that MnV₁₃ modified perovskite photodetector has the best efficiency. The photocurrent increased from 26 μA to 80 μA. Its stability is good. After 720 hours, the normalized current values of unencapsulated devices on MnV₁₃@SnO₂substrate still maintain more than 70% of the initial values. This work shows that introducing POVs into photodetectors is a potential strategy to optimize the performance of photovoltaic devices.