Tailoring the Interface in FAPbI3 Planar Perovskite Solar Cells by Imidazole-Graphene-Quantum-Dots

Organic–inorganic hybrid perovskites have reached an unprecedented high efficiency in photovoltaic applications, which makes the commercialization of perovskite solar cells (PSCs) possible. In the past several years, particular attention has been paid to the stability of PSC devices, which is a critical issue for becoming a practical photovoltaic technology. In particular, the interface-induced degradation of perovskites should be the dominant factor causing poor stability. Here, imidazole bromide functionalized graphene quantum dots (I-GQDs) are demonstrated to regulate the interface between the electron transport layer (ETL) and formamidinium lead iodide (FAPbI) perovskite layer. The incorporation of I-GQDs not only reduces the interface defects for achieving a better energy level alignment between ETL and perovskite, but also improves the film quality of FAPbI perovskite including enlarged grain size, lower trap density, and a longer carrier lifetime. Consequently, the planar FAPbI PSCs with I-GQDs regulation achieve a high efficiency of 22.37% with enhanced long-term stability.