Surface Recovery of Perovskite Quantum Dots via Covalent Ligand Solution Dissolved in Nonpolar Solvent
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Ligand exchange of CsPbI3 perovskite quantum dots (PQDs) enables the fabrication of CsPbI3 PQD absorbers for efficient solar cell. However, surface trap sites on the PQD surfaces which are generated during the ligand exchange process deteriorate the film properties of CsPbI3 absorber. Here, surface recovery strategy is demonstrated for improving the photovoltaic properties and stability of CsPbI3 PQD absorber using covalent phosphine oxide ligand solution dissolved in nonpolar solvent. Covalent ligand can efficiently passivate the surface trap sites via Lewis-base interaction and the nonpolar solvent can suppress the additional surface trap sites generation. Through the synergetic effect of strong covalent ligand and stable solvent, the PQD surfaces are efficiently recovered. Consequently, the CsPbI3 PQD solar cells treated with the covalent ligand solution dissolved in nonpolar solvent show better photovoltaic performance and stability.