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

Abstract

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 TEAPF₆ into perovskite films as an excellent additive. TEAPF₆ 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. TEAPF₆ 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 TEAPF₆ achieved a PCE of 22.13%. Moreover, TEAPF₆ 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.