Tuning the Surface-Passivating Ligand Anchoring Position Enables Phase Robustness in CsPbI3 Perovskite Quantum Dot Solar Cells

Cubic CsPbI3 perovskite quantum dots (PQDs) with ideal optoelectronic properties are promising materials for solution-processed photovoltaics. However, their phase stability suffers from the weakly bound surface ligands. Here, we report the adoption of p-mercaptopyridine ligand post-treatment on PQDs and obtained enhanced electronic coupling and cubic phase robustness in comparison with the treatment using analogous o-mercaptopyridine and pyridine ligands. As a result, CsPbI3 PQDs solar cells achieved an efficiency of 14.25%. More importantly, the device stability was drastically improved, showing decent efficiency after storage under ambient conditions for similar to 70 days. We revealed that tuning of the anchoring position can facilely enhance the ligand binding strength and surface coverage, providing efficient ways to significantly improve the performance and stability of PQD-based optoelectronic devices.