Synergistic dual-surface passivation via 1-butyl-3-methylimidazolium iodide for efficient and stable inverted CsPbI₂Br perovskite solar cells.

Authors

Xin Liu, Chengguo Liu, Lang Wang, Quzhen Zhaxi, Tingting Hou, Shu Wang, Xiaoxuan Li, Wangyang Song, Xingyue He, Weifan Luo, Dingyu Yang

Published in

RSC advances. Jul 03, 2026. Epub Jul 03, 2026.

Abstract

All-inorganic CsPbI₂Br perovskites have garnered significant interest for their superior thermal stability and suitable bandgap, rendering them promising candidates for tandem and indoor photovoltaics. However, the pronounced non-radiative recombination losses at both the buried hole transport layer (HTL)/perovskite and the top perovskite/electron transport layer (ETL) interfaces severely curtail the power conversion efficiency (PCE) of inverted p-i-n architecture devices. Herein, we systematically elucidate the distinct interfacial modification roles of imidazolium-based ionic liquids (ILs) with varying halide anions, 1-butyl-3-methylimidazolium iodide (BMIMI), bromide (BMIMBr), and chloride (BMIMCl). Density functional theory (DFT) calculations reveal that BMIMBr and BMIMCl unexpectedly lower the formation energy of iodine vacancies (V _I) in CsPbI₂Br, paradoxically promoting detrimental defect formation, whereas BMIMI maintains a benign profile and powerfully passivates both cationic and anionic defects through synergistic Lewis acid-base interactions. We decouple the effects of single- and dual-interface modification: bottom-interface BMIMI treatment predominantly enhances fill factor (FF) by improving hole extraction and perovskite crystallization, while top-interface modification substantially elevates open-circuit voltage (V _oc) through effective surface defect passivation. Consequently, the synergistic dual surface modification (DSM) with BMIMI yields a champion PCE of 15.28% for inverted CsPbI₂Br devices, representing a 23.12% enhancement over the control device (12.41%). The DSM devices exhibit a substantially mitigated hysteresis index of 2.03% and retain 91% of their initial efficiency after 2100 h of nitrogen storage.

PMID:
42405046
Bibliographic data and abstract were imported from PubMed on 06 Jul 2026.

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