An ionic liquid as an interface modulator for highly efficient and stable perovskite solar cells

Abstract

Perovskite solar cells (PSCs) are emerging technologies that have been heavily researched due to their outstanding photoelectric properties. However, the majority of recombination losses occur at the interface between perovskite and the ETL, resulting in their full potential not yet being reached. In this work, ionic liquid (IL) 1-buty-3-methylimidazole hydrogensulfate (BMIMHSO₄) was employed to regulate the TiO₂/perovskite interface. BMIMHSO₄ formed a surface dipole, which realigned the TiO₂ conduction band upward, allowing for faster charge extraction, and lower energy loss at the interface. Furthermore, the BMIMHSO₄ induced a vertical crystal arrangement, decreased the perovskite defect density, and reduced the defect-induced charge recombination in MAPbI₃-based PSCs. Consequently, the power conversion efficiency (PCE) was improved from 15.92% to 19.13%. Moreover, the un-encapsulated device exhibited improved stability and retained 90% of its original value after 600 storage hours. This work demonstrated a practical technique to optimize the interface by applying an IL, thus achieving high-performance PSCs.