Grain Boundary Engineering with Cl-Terminated Ti2C Quantum Dots for Enhancing Perovskite Solar Cell Performance

The power conversion efficiency and stability of polycrystalline perovskite solar cells are compromised by grain-boundary-dominated ion migration. Herein, the grain boundaries of CH₃NH₃PbI₃ films were engineered using Ti₂C quantum dots. Ti₂C quantum dots had a strong interaction with Pb²⁺ and I^– ions, which retarded crystal growth, resulting in larger grain size and less grain boundary in perovskite films. Additionally, the Ti₂C quantum dots at the grain boundary could anchor ions and passivate defects, increasing activation energy for ion hopping and reducing trap density. In consequence, perovskite films were used to fabricate solar cells with significantly improved efficiency and stability. These findings may allow the development of versatile grain boundary modifiers for perovskite optoelectronic devices that combine stability and efficiency.