High-Efficiency Perovskite Solar Cells with Oriented Growth and Consolidated ABX3 Structures via Multifunctional Ionic Liquids at Buried Interfaces.

Abstract

Although perovskite solar cells (PSCs) are advancing rapidly, a series of issues including interfacial nonradiative recombination losses continue to constrain their photovoltaic performance. Herein, a multifunctional fluorinated pseudohalide ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMTFSI) is introduced at the buried interface to passivate the interfacial defect and consolidate the perovskite ABX₃ structure effectively. The results reveal that the fluorine and sulfonyl groups on EMIMTFSI can passivate the oxygen vacancy defects in the SnO₂ layer, thereby enhancing the interfacial contact and effectively suppressing the nonradiative charge recombination. In addition, EMIMTFSI facilitates the oriented growth of perovskite along the (110) plane and promotes the enlargement of perovskite grains. Furthermore, the anionic TFSI^- and cationic EMIM⁺ ions stabilize the perovskite ABX₃ structure by filling X-vacancy defects in the perovskite crystals and by coordinating them with uncoordinated Pb²⁺ defects. Hence, the W EMIMTFSI device exhibits a significant increase in power conversion efficiency from 20.74% to 22.73% and obtains an excellent long-term stability. This study presents a possible innovative way to achieve a highly efficient and stabilizing PSC by EMIMTFSI multifunctional modifications at buried interfaces.