Efficient and Stable CsPbI₂Br Inorganic Perovskite Solar Cell Co-Modified with Ionic Liquids and Quantum Dots

The all-inorganic CsPbI2Br perovskite possesses outstanding thermal stability as a light absorber in perovskite solar cells (PSCs) or photodetectors. Still, their sensitivity to moisture induces irreversible decomposition and a large number of halogen vacancy defects, hindering their commercial applications. Herein, by incorporating 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) ionic liquids (ILs) as a precursor additive, a CsPbI2Br light absorber with an improved carrier lifetime and reduced trap density is achieved. Moreover, the modification of the perovskite surface with CsPbBr3 quantum dots (QDs) further improved the efficiency and moisture stability of the PSC. As a result, the BMIMBF4 IL and CsPbBr3 QD co-modified PSC achieves a maximum power conversion efficiency (PCE) of 15.37% and retained 80% of its initial PCE after exposure to ambient air for 60 h. This work proposes a synergistic approach for developing high-performance organic-free PSCs with an improved PCE and moisture stability.