Effect of isomeric hole-transporting materials on perovskite solar cell performance

As an important component of perovskite solar cells (PSCs), hole transport materials (HTMs) are of great significance to improve the efficiency and long-term stability of PSCs. When designing HTMs, hole mobility is an important concern; meanwhile, the ability to passivate defects in perovskite has to be taken into consideration. Herein, we introduced dipyridyl ketone as the core moiety to construct two isomers XJ2 and XJ3. The two isomers are distinguished by the position of the carbonyl group with respect to the N atom on the pyridine ring. Studies show that different positions of the CO group result in different electronic properties of the two isomers. The meta substitution of the carbonyl group in XJ2 endows it with a lower energy level and higher hole mobility compared with its counterpart XJ3. Such rational design also endows the defect passivation ability, and XJ2 exhibits a stronger passivation effect due to the smaller steric hindrance effect. As a result, the power conversion efficiency (PCE) of the XJ2-based device reaches 20.17%, which is much higher than the device with XJ3 as the HTM (18.84%).