Moisture-preventing MAPbI₃ solar cells with high photovoltaic performance via multiple ligand engineering

Perovskite solar cells present one of the most prominent photovoltaic technologies, yet their stability, and engineering at the molecular level remain challenging. We have demonstrated multifunctional molecules to improve the operating stability of perovskite solar cells while depicting a high-power conversion efficiency. The multifunctional molecule 4-[(trifluoromethyl) sulphanyl]-aniline (4TA) with trifluoromethyl (-CF₃) and aniline (-NH₂) moieties is meticulously designed to modulate the perovskite. The -CF₃ and -NH₂ functional groups have strong interaction with perovskite to suppress surface defects to improve device stability, as well as obtain large crystal grains through delaying crystallization. Moreover, this -CF₃ forms a hydrophobic barrier on the surface of the perovskite to prevent cell decomposition. Consequently, the performance of the perovskite solar cells is remarkably improved with the efficiency increased from 18.00% to 20.24%. The perovskite solar cells with multifunctional molecular maintaining 93% of their original efficiency for over 30 days (~ 55% humidity) in air without device encapsulation, exhibiting a high long-term stability. Moreover, the lead leakage issue of perovskite solar cells has also been suppressed by the built-in 4TA molecule, which is beneficial to environment-friendly application. Ultimately, we believe this multifunctional small molecule provides an available way to achieve high performance perovskite solar cells and the related design strategy is helpful to further develop more versatile materials for perovskite-based optoelectronic devices.