ABSTRACT The energy level mismatch and defect‐induced recombination at the SnO 2 /perovskite interface limit the performance of perovskite solar cells. Herein, we comprehensively compare the multifunctional pyridine derivatives 3‐amino‐pyridine (3‐AP), 5‐amino‐2‐fluoropyridine (5‐A2FP), and 5‐amino‐2‐fluoro‐4‐pyridic acid (5‐A2F4PCA) as molecular bridges to suture interface defects and optimize energy level alignment. In these pyridine derivatives, 3‐AP molecule with a rigid planar conjugated pyridine ring provides a single amino group (─NH 2 ) to passivate the defect on SnO 2 surface; further 5‐A2FP molecule inserts a fluorine group (─F) to polarize the interface and regulate the energy level; furthermore 5‐A2F4PCA molecule adds a carboxyl group (─COOH) to coordinate positive charged vacancy and guide perovskite crystallization. From the single passivation of ─NH 2 group in 3‐AP, to the superposition of ─NH 2 and ─F groups in 5A‐2FP, and to the synergy of ─NH 2 , ─F, and ─COOH groups in 5‐A2F4PCA, the molecular bridging effect gradually strengthens, this strategy realizes multiple improvements from the crystallization control, defect passivation, to energy level optimization. The 5‐A2F4PCA‐optimized device achieves a champion power conversion efficiency of 25.82%, while retaining 92% efficiency after 1200 h of maximum power point tracking. This work demonstrates the synergistic effect of multifunctional bridging molecules in interface regulation.
Wang et al. (Wed,) studied this question.