Multifunctional potassium hexafluorophosphate passivate interface defects for high efficiency perovskite solar cells

The interface modulation between perovskite and carrier-transport layers via an appropriate chemical bond is an effective way to achieve the promoted carrier extraction and the reduced charge recombination for high-efficiency perovskite solar cells (PSCs). Here, a multifunctional material potassium hexafluorophosphate (KPF6) is employed as an effective interface material between SnO2 quantum dots (QDs) and perovskite. At perovskite side, KPF6 could react with perovskite through the strong hydrogen bonds between PF6− group and organic cations, which could re-orientate or redistribute the organic cation groups. Meanwhile, KPF6 could react with SnO2 QD through the strong ionic bonds between PF6− group and Sn4+/Sn2+ at the SnO2 QD side, which could passivate the interface defects to suppress the non-radiative recombination for the improved electron-transferring. Consequently, a champion PCE over 21% comes from the PSCs with 0.5 mg/ml KPF6 treated the SnO2 QD/perovskite interface, and the devices maintain ~90% of initial PCEs after 720-h storage in dry air.