Efficiency enhancement to 24.62% in inverted perovskite solar cells through poly (ionic liquid) bulk modification

Small-molecule ionic liquids (ILs) are frequently employed as efficient bulk phase modifiers for perovskite materials. However, their inherent characteristics, such as high volatility and ion migration properties, pose challenges in addressing the stability issues associated with perovskite solar cells (PSCs). Here, we design a poly (IL) with multiple active sites, named poly[4-styrenesulfonyl(trifluoromethylsulfonyl)imide]pyridine (P[STFSI][PPyri]), as an efficient additive of perovskite materials. The S=O in the sulfonyl group chelates with uncoordinated Pb²⁺ and forms hydrogen bonds with the organic cations in perovskite, suppressing the volatilization of organic cations. N⁺ in the pyridine can fix halide ions through electrostatic interaction with I⁻, Br⁻ ions to prevent halide ions migration. P[STFSI][PPyri] demonstrates the ability to passivate defects and suppress non-radiative recombination in PSCs. Additionally, it facilitates the fixation of organic ions and halide ions, thereby enhancing both the photoelectric performance and stability of the device. Consequently, the introduction of P[STFSI][PPyri] as a dopant in the devices results in a champion efficiency of 24.62%, demonstrating outstanding long-term operational stability, with the encapsulated device maintaining 87.6% of its initial efficiency even after 1500 hours of continuous maximum power point tracking. This strategy highlights the promising potential of poly (IL) as an effective additive for PSCs, providing a combination of high performance and stability.