Ultrathin Dimethylammonium Iodide Matrix: Suppressing Octahedral Distortion and Reconstructing Surface Ligands for Efficient CsPbI3 Quantum Dot Photovoltaics

Inorganic CsPbI 3 quantum dots (QDs) have received increasing attention for their application in new‐generation solar cells. However, their poor phase stability due to the small ionic radius of Cs and their inhomogeneous energy landscape on the QD surface during ligand exchange remain as bottlenecks for the practical application of CsPbI 3 QD photovoltaics. Herein, the unfavorable octahedral distortion is effectively suppressed by riveting dimethylammonium hydroiodide (DMAI) into the lattice structure. Moreover, DMAI reconstructs the surface ligands to create an ultrathin matrix that encloses the QDs. The ultrathin DMAI matrix effectively passivates the vacancy defects and allows efficient coupling and charge transport in the QD films. As a result, the CsPbI 3 QD solar cell yields an efficiency approaching 15%. In addition, the increase in the Goldschmidt tolerance factor enhances the stability of the octahedral structure, resulting in significantly improved device stability.