Interface modification by formamidine acetate for efficient perovskite solar cells

Perovskite solar cells (PSCs) have received widespread attention due to their excellent photovoltaic characteristics. However, the nonradiative recombination of carriers induced by defects limits the stability and performance of PSCs. Interface and additive engineering are good medicine to cure the disease. Herein, formamidine acetate (FAAc) as interfacial additive is introduced to the TiO2/perovskite interface. The connection of the FA+ between the TiO2 and perovskite promotes electron transport, and the amino group (−NH2) and carboxyl group (−COOH) of FAAc passivates the defect at TiO2/perovskite interface. Meanwhile, the FAAc modification tunes the energy array and improves crystal quality of perovskite. In consequence, the PSC based on FAAc-modified TiO2 achieves the best power conversion efficiency (PCE) of 20.47%, accompanied with excellent stability and mitigated hysteresis, while PCE of the pristine PSC is 18.30%.