All‐Inorganic CsPbI3 Quantum Dot Solar Cells with Efficiency over 16% by Defect Control

Abstract All‐inorganic CsPbI 3 quantum dots (QDs) have shown great potential in photovoltaic applications. However, their performance has been limited by defects and phase stability. Herein, an anion/cation synergy strategy to improve the structural stability of CsPbI 3 QDs and reduce the pivotal iodine vacancy ( V I ) defect states is proposed. The Zn‐doped CsPbI 3 (Zn:CsPbI 3 ) QDs have been successfully synthesized employing ZnI 2 as the dopant to provide Zn 2+ and extra I − . Theoretical calculations and experimental results demonstrate that the Zn:CsPbI 3 QDs show better thermodynamic stability and higher photoluminescence quantum yield (PLQY) compared to the pristine CsPbI 3 QDs. The doping of Zn in CsPbI 3 QDs increases the formation energy and Goldschmidt tolerance factor, thereby improving the thermodynamic stability. The additional I − helps to reduce the V I defects during the synthesis of CsPbI 3 QDs, resulting in the higher PLQY. More importantly, the synergistic effect of Zn 2+ and I − in CsPbI 3 QDs can prevent the iodine loss during the fabrication of CsPbI 3 QD film, inhibiting the formation of new V I defect states in the construction of solar cells. Consequently, the anion/cation synergy strategy affords the CsPbI 3 quantum dot solar cells (QDSC) a power conversion efficiency over 16%, which is among the best efficiencies for perovskite QDSCs.