Renovating the surface matrix of FAPbl₃ perovskite quantum dots via phase-transfer catalysis for 16.29% efficiency solar cells

Formamidinium lead triiodide perovskite quantum dots (FAPbI₃ PQDs) draw remarkable research interest for the development of new-generation solar cells. However, the FAPbI₃ PQD suffers from serious trap-assisted charge carrier recombination due to its defective surface matrix, which mainly results from the detachment of oleic acid/oleylamine ligands from the PQD surface during the purification of the PQDs using the antisolvent, predominantly affecting the photovoltaic performance and operational stability of PQD solar cells (PQDSCs). Herein, a facile phase-transfer catalysis (PTC) approach is reported to renovate the defective surface matrix of PQDs for efficient PQDSCs. During the PTC treatment of PQDs, 3-(trifluoromethyl) phenyltrimethylammonium iodide (3-CF₃-PTAI) could form a 3-CF₃-PTAI/formamidinium iodide (FAI) complex with the FAI to transfer FAI from the polar solvent to nonpolar solvent, which could subsequently fill FA⁺/I⁻ vacancies at the defective surface matrix of PQDs, thus effectively renovating the surface matrix and substantially suppressing the trap-assisted recombination of PQDs. Meanwhile, the stacking orientation of the PQDs within the PQD solids was also predominantly ameliorated due to the effectively healed surface matrix and extensively removed oleic acid/oleylamine ligands of PQDs, facilitating charge carrier transport within the PQD solids. Consequently, the FAPbI₃ PQDSC gave a power conversion efficiency of up to 16.29%, which is largely improved compared with the control PQDSC with an efficiency of 13.21%. This work provides important design principles and a new avenue to reconstruct the surface matrix of PQDs for high-performance photovoltaics.