g-C3N4@PMo12 composite material double adjustment improves the performance of perovskite-based photovoltaic devices

Abstract At present, reducing the defect density at grain boundaries is still the main method to improve the performance of perovskite photodetectors. The increase of grain size can also improve the performance of perovskite photodetectors. In this work, we added POM @ g-C3N4 as a dopant into the perovskite precursor solution for the first time. The doping of g-C3N4 can control the crystallization rate of perovskite, thereby passivating the charge recombination center at the grain boundary to reduce the defect density. However, the conduction band energy level of g-C3N4 is higher than that of perovskite, which is not conducive to electron transmission. Polyoxometalate (POM) H3PMo12O40 (PMo12) has very good ultraviolet–visible light absorption. Adding it to perovskite can improve the ultraviolet–visible light absorption of the perovskite layer. Furthermore, the energy level of the polyoxometalate PMo12 matches the perovskite layer, which promotes the electron transport. Adding the composite material to the perovskite precursor solution not only increases the grain size of the perovskite crystals from 100 nm to 300 nm, but also increases the light absorption of the perovskite layer. Consequently, the photocurrent increased from 4.5 μA to 11.5 μA under the double regulation of the composite material, which is 2.6 times of the photocurrent of the reference group. This work provides a method of double adjustment of composite materials to increase the photocurrent of photodetectors.