Tuning 2D Perovskite Passivation: Impact of Electronic and Steric Effects on the Performance of 3D/2D Perovskite Solar Cells

• Published in: Advanced energy materials Vol. 13; no. 45
• Main Authors: Gozukara Karabag, Zeynep, Karabag, Aliekber, Gunes, Ummugulsum, Gao, Xiao‐Xin, Syzgantseva, Olga A., Syzgantseva, Maria A., Varlioglu Yaylali, Figen, Shibayama, Naoyuki, Kanda, Hiroyuki, Rafieh, Alwani Imanah, Turnell‐Ritson, Roland C., Dyson, Paul J., Yerci, Selcuk, Nazeeruddin, Mohammad Khaja, Gunbas, Gorkem
• Format: Journal Article
• Language: English
• Published: 01.12.2023
• Subjects: 3D/2D perovskite solar cells; phenylethylammonium cations; power conversion efficiency; stability; substituent and position effects
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.202302038

Surface 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%, (VOC=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. 3D/2D structured PSCs, realized with phenylethylammonium iodide based salts (x‐XPEAI; x: o, m, p; X: F, Cl, Br), that are synthesized by simple three‐step method, have significant impact on photovoltaic device performance and stability. It is shown that salts substituted at meta positions with halogens outperform their ‐o and ‐p analogs independent of the halogen type due to favorable surface dipoles supported by detailed density functional theory analyses.