Defect Passivation with 4-(Trifluoromethyl)Aniline for Efficient and Stable FAPbI3 Quantum Dot Solar Cells

Conventional ligand exchange strategies for FAPbI3 quantum dots (QDs) rely on polar solvents, which compromise colloidal stability and device performance. Herein, a ligand-mediated defect passivation strategy is proposed, in which 4-(trifluoromethyl)aniline (4-ATFB) is incorporated into the toluene-based solvent system during the purification of FAPbI3 QDs. The amino group of 4-ATFB coordinates with undercoordinated Pb2+ sites to passivate defects and optimize FA+ charge distribution, while outward-oriented trifluoromethyl group forms a barrier against moisture. The dual functionality stabilizes the lattice and suppresses defects during the purification process. Moreover, the carrier dynamics are significantly improved with 4-ATFB treatment, attributed to reduced defect density and suppressed trap-mediated losses, leading to enhanced radiative recombination. Consequently, the fabricated FAPbI3 QDs solar cells with 4-ATFB treatment exhibit a champion power conversion efficiency of 16.33%, representing a significant improvement over the control device (14.99%), together with exceptional operational stability that retains over 80% of the initial efficiency after 25 days of storage in an ambient atmosphere without encapsulation.