Heteropoly Blue Modified SnO₂ for Highly Efficient Perovskite-Based Photodetectors

Due to the higher electrical conductivity, SnO2 becomes a promising material for electron transport layers (ETLs). However, the mismatched energy level and surface defects lead to unsatisfactory contact between the perovskite film and SnO2 layer, which limits its further application. Herein, heteropoly blue (HPB) r-PMo12–xVx (x = 0, 1, 2) is chosen to modify the interface contact between the perovskite layer and the SnO2 layer. The energy level of HPB-modified SnO2 increases from −4.49 to −4.09 eV, which is more suitable with the perovskite layer, thus improving the electron transport. In addition, the introduction of HPBs reduces the oxygen defects on the surface of SnO2, while metal–oxygen bonding in the HPBs can improve the quality of the perovskite film by passivation. As a result, the photocurrent of the photodetector increases from 22.4 to 81.7 μA, an enhancement of about 3.6 times. In particular, the HPB-modified photodetector can still maintain 90% of the initial performance after 700 h and the stability is significantly improved, providing a good idea for efficient and stable perovskite photodetectors.