Spatially Isomeric Fulleropyrrolidines Enable Controlled Stacking of Perovskite Colloids for High-Performance Tin-Based Perovskite Solar Cells.

The advancement of tin-based perovskite solar cells (TPSCs) has been severely hindered by the poor controllability of perovskite crystal growth and the energy level mismatch between the perovskite and fullerene-based electron transport layer (ETL). Here, we synthesized three cis-configured pyridyl-substituted fulleropyrrolidines (PPF), specifically 2-pyridyl (PPF2), 3-pyridyl (PPF3), and 4-pyridyl (PPF4), and utilized them as precursor additives to regulate the crystallization kinetics during film formation. The spatial distance between the two pyridine groups in PPF2, PPF3, and PPF4 increases sequentially, enabling PPF4 to interact with more perovskite colloidal particles.