Ionic-Liquid-Assisted Fabrication of High-Performance Methylammonium-Free Perovskite Solar Cells via Smoothed-Interface Engineering

Abstract

A judicious modification of the buried interface can enhance the quality of perovskite films and reduce non-radiative recombination losses, particularly in methylammonium (MA)-free perovskite solar cells (PSCs). In this study, the ionic-liquid 1,3-dimethylimidazolium methanesulfonate (DMIMMeSO4) is employed, characterized by its high ionic conductivity and excellent thermal stability, to regulate the perovskite/SnO2 interface. The nitrogen component in DMIMMeSO4 can interact with Sn4+ through Lewis acid–base interactions, effectively passivating defects associated with tin and suppressing the formation of oxygen vacancies, leading to reduced non-radiative recombination of charge carriers. In addition, [MeSO4]− can also form coordination bonds with PbI2, creating a better perovskite film with smoothed interface. Moreover, DMIMMeSO4 also optimize the energy-level alignment, thereby reducing the charge-transfer barrier and enhancing charge-extraction efficiency. As a result, power conversion efficiency of 23.91% is achieved by MA-free PSCs modified with DMIMMeSO4. Furthermore, after 1000 h of ambient air storage, devices that are not encapsulated maintaine over 90% efficiency. In all of these results, it is clearly indicated that interface modulation based on ionic-liquid-assisted smoothed-interface engineering is an effective approach for obtaining high-performance PSCs.