Karabag, Zeynep GozukaraKarabag, AliekberGunes, UmmugulsumGao, Xiao-XinSyzgenteva, Olga A.Syzgenteva, Maria A.Varlioglu Yaylali, FigenShibayama, NaoyukiKanda, HiroyukiRafieh, Alwani ImanahTurnell-Ritson, Roland C.Dyson, Paul J.Yerci, SelcukNazeeruddin, Mohammad KhajaGunbas, Gorkem2023-10-232023-10-232023-10-232023-10-0310.1002/aenm.202302038https://infoscience.epfl.ch/handle/20.500.14299/201811WOS:001076964700001Surface passivation with 2D perovskites is a powerful strategy to achieve improved stability and performance in perovskite solar cells (PSCs). Various large organic cations have been successfully implemented, led by phenylethylammonium (PEA+) and its derivatives. However, systematic studies on large sets of cations to understand the effect of substituent position on 2D perovskite passivation and device performance are lacking. Herein, a collection of halogenated PEA+ iodide salts (x-XPEAI where x: ortho (o), meta (m), para (p), X: F, Cl, Br) are synthesized by a facile method and deposited on top of 3D perovskite. The 2D perovskite layer formation is confirmed by X-ray diffraction (XRD) and grazing-incidence wide-angle X-ray scattering analyses for all cations, regardless of the nature and position of the halogen. Density functional theory analysis reveals that lower formation energies and higher interfacial dipoles achieved by m-substituted cations are responsible for enhanced performance compared to their o- and p- counterparts. While the m-BrPEAI-treated device shows a champion efficiency of 23.42%, (V(OC)=1.13 V, FF=81.2%), considering average efficiencies, stability, and reproducibility, the treatment with m-ClPEAI salt yields the best overall performance. This comprehensive study provides guidelines for understanding the influence of large cation modification on performance and stability of 3D/2D PSCs.Chemistry, PhysicalEnergy & FuelsMaterials Science, MultidisciplinaryPhysics, AppliedPhysics, Condensed MatterChemistryEnergy & FuelsMaterials SciencePhysics3d/2d perovskite solar cellsphenylethylammonium cationspower conversion efficiencystabilitysubstituent and position effectsefficientcationsiodidetext::journal::journal article::research article