Tailoring solvent-mediated ligand exchange for CsPbI3 perovskite quantum dot solar cells with efficiency exceeding 16.5%

•Tailored solvent maximizes the removal of insulating ligands from the PQD surface •Tailored solvent mediates short ligands to adequately bind to the PQD surface •Solvent-mediated ligand exchange improves the defect passivation of PQDs Inorganic CsPbI3 perovskite quantum dot (PQD) shows high potential for new-generation photovoltaics due to its outstanding optoelectronic properties. However, the binding-energy-driven ligand exchange of PQDs limits the construction of conductive and stable PQD solids for efficient PQD solar cells (PQDSCs). Herein, protic 2-pentanol with superior ligand solubility is delicately screened from massive solvents to mediate the ligand exchange of PQDs due to its appropriate dielectric constant and acidity, which could maximize the removal of pristine insulating oleylamine ligands from the PQD surface without introducing halogen vacancy defects. Employing tailored short choline ligands and 2-pentanol solvent for the post-treatment of PQD solids, PQDSC yields an efficiency of 16.53%, which is the highest among inorganic PQDSCs. This outstanding performance is attributed to the improved charge carrier transport and surface defect passivation of PQDs. This work provides a feasible platform for tuning the surface properties of PQDs and paves the way for realizing high-performing optoelectronics. Inorganic CsPbI3 perovskite quantum dot (PQD) shows high potential for new-generation photovoltaics due to its outstanding optoelectronic properties. However, the binding-energy-driven ligand exchange of PQDs limits the construction of conductive and stable PQD solids for efficient PQD solar cells (PQDSCs). Herein, protic 2-pentanol with superior ligand solubility is delicately screened from massive solvents to mediate the ligand exchange of PQDs due to its appropriate dielectric constant and acidity, which could maximize the removal of pristine insulating oleylamine ligands from the PQD surface without introducing halogen vacancy defects. Employing tailored short choline ligands and 2-pentanol solvent for the post-treatment of PQD solids, PQDSC yields an efficiency of 16.53%, which is the highest among inorganic PQDSCs. This outstanding performance is attributed to the improved charge carrier transport and surface defect passivation of PQDs. This work provides a feasible platform for tuning the surface properties of PQDs and paves the way for realizing high-performing optoelectronics.