Multifunctional pseudohalide-based ionic liquid doping promotes efficient and stable perovskite solar cells

High-quality perovskite films are crucial to realizing high-efficiency stable perovskite solar cells. Doping is a direct and effective strategy to passivate defects and improve the crystal quality of perovskite films. Herein, we introduce pseudohalide-based ionic liquid TEAPF(6) into perovskite films as an excellent additive. TEAPF(6) doping has multiple effects: the PF6- anion could fill the halide vacancies, which helps to suppress ion migration through vacancies. The highly electronegative PF6- could bind with uncoordinated Pb2+ and organic cations to passivate defects. TEAPF(6) doping improved the crystal quality and suppressed the charge recombination in perovskite films. More importantly, the TEA(+) with long alkyl groups and PF6- could enhance the hydrophobicity of the perovskite films. As a result, the device with TEAPF(6) achieved a PCE of 22.13%. Moreover, TEAPF(6) doping enhanced the stability of PSCs. This work demonstrates the excellent effect of pseudohalide-based ionic liquid doping on improving the crystal quality of perovskite films.