Ligand-Assisted Coupling Manipulation for Efficient and Stable FAPbI 3 Colloidal Quantum Dot Solar Cells.

For emerging perovskite quantum dots (QDs), understanding the surface features and their impact on the materials and devices is becoming increasingly urgent. In this family, hybrid FAPbI QDs (FA: formamidium) exhibit higher ambient stability, near-infrared absorption and sufficient carrier lifetime. However, hybrid QDs suffer from difficulty in modulating surface ligand, which is essential for constructing conductive QD arrays for photovoltaics. Herein, assisted by an ionic liquid formamidine thiocyanate, we report a facile surface reconfiguration methodology to modulate surface and manipulate electronic coupling of FAPbI QDs, which is exploited to enhance charge transport for fabricating high-quality QD arrays and photovoltaic devices. Finally, a record-high efficiency approaching 15 % is achieved for FAPbI QD solar cells, and they retain over 80 % of the initial efficiency after aging in ambient environment (20-30 % humidity, 25 °C) for over 600 h.