High-effective SnO2-based perovskite solar cells by multifunctional molecular additive engineering

•3-(formamidinothio)-1-propanesulfonic acid (FTPS) is used as additives of SnO2.•FTPS improves crystal quality and conductivity, reduces defects and recombination.•FTPS doped device achieves a power conversion efficiency of 22.52%.•While the controlled device obtains an efficiency of 20.49% at the same condition. The electron transport layer (ETL) is one of the most important factors to determine the photovoltage (PV) performance of perovskite solar cells (PSCs), and defects and non-radiative recombination are the negative factors limiting the efficiency improvement of PSCs. Herein, using tin oxide (SnO2) as the electron transport layer and multiple functional groups organic molecule of 3-(formamidinothio)-1-propanesulfonic acid (FTPS) as additive of SnO2, we fabricated a high-effective SnO2-based planar PSC. The introduction of FTPS reduces the oxygen vacancy defects of SnO2 ETLs and accommodates perovskite crystal growth on it. The modification of FTPS improves the conductivity and the electron extraction ability of SnO2, mitigates the trap-state density and carrier non-radiative recombination at the interfaces of SnO2/perovskite. As a result, the PSC based on pristine SnO2 ETL obtains a power conversion efficiency (PCE) of 20.49%, while the champion device based on SnO2 + FTPS (0.3 mg/mL) ETL achieves an efficiency of 22.52% with insignificant hysteresis effect and excellent stability. This effective defect passivation strategy work provides a promising low-cost technology for the preparation of planar PSCs with high efficiency and stability.