Multifunctional Surface Modulation of CsPbI3 Nanocrystals Enables Stable and Efficient Quantum Dot Solar Cells

All-inorganic CsPbI3 perovskite quantum dots (PQDs) represent a class of highly promising materials for next-generation photovoltaics. However, their stability is hindered by surface structural defects—primarily arising from dynamic ligand detachment—which severely compromise the stability of both the PQDs and their resulting thin films. In this study, we implement a multifunctional surface modification (MSM) strategy by introducing mono-butylammonium tetrafluoroborate (MBT) molecules to selectively passivate these surface vacancies. This approach not only stabilizes the PQD structure but also facilitates enhanced interdot electronic coupling, resulting in films with significantly reduced defect densities and improved energetic uniformity. Consequently, the MSM-treated device achieves a PCE of 15.5%, a substantial improvement over the 13.5% recorded for control devices, while exhibiting superior environmental stability. This work provides mechanistic insights into surface stabilization of CsPbI3 PQDs through a multifunctional surface modulation strategy, enabling enhanced performance and stability of PQD solar cells.