Synergistic Interfacial Passivation and Dipole-Field Engineering for Enhanced Charge Extraction in CsPbI ₃ Perovskite Quantum Dot Solar Cells

Perovskite quantum dot (PQD) solar cells based on CsPbI3 have attracted considerable attention owing to their excellent optoelectronic properties. Continuous progress in ligand engineering has significantly improved their power conversion efficiency. However, limited attention has been paid to the hindered charge transport between the electron transport layer and the PQD layer caused by vacancy defects at the interface. Here, 6-aminonicotinic acid (AMC) molecules are introduced as a multifunctional interfacial modifier between the TiO2 ETL and the PQD layer to simultaneously passivate oxygen-vacancy defects and induce dipole-field-assisted interlayer charge transport. Experimental characterization and density functional theory calculations demonstrate that AMC molecules not only effectively passivate oxygen vacancies on the TiO2 surface but also accelerate electron extraction by regulating the interfacial energy-level alignment through dipole-field effects. Furthermore, interfacial modulation by AMC improves the crystallographic orientation and film uniformity of the PQD layer. As a result, the device efficiency is enhanced from 13.1 to 15%. This work provides an effective interfacial engineering strategy for improving charge transport and device performance in PQD solar cells.