Halogen substitution of perinone-based cathode interfacial materials for high-efficiency inverted perovskite solar cells

The development of cathode interfacial materials (CIMs) is one of the most effective ways to improve the performance of perovskite solar cells (PSCs). In inverted PSCs, CIMs lag behind in terms of the quick increase of the power conversion efficiency (PCE). In this study, we designed and synthesized two perinone-based CIMs, NX-F and NX-Cl and successfully applied them to inverted PSCs. Four fluorine and chlorine atoms were introduced into the perinone core of NX-F and NX-Cl, respectively. Compared to the NX-Cl film, the NX-F film possesses a lower LUMO level, stronger pi-pi stacking and higher electron mobility. The inverted PSCs with NX-F as the CIM achieve a champion PCE of 21.18%, which is higher than that of NX-Cl devices (20.25%) and control devices (19.42%). The superior PCE of the NX-F devices is accompanied by the improvement of all parameters. Further investigation demonstrates that the NX-F devices exhibit the lowest trap density and recombination and the best charge transfer and transport. The PSCs with NX-F and NX-Cl also show fine storage stabilities in nitrogen and humid air atmospheres. A fluorine-substituted perinone derivative exhibits better cathode interfacial modification than the chlorine-substituted one in inverted perovskite solar cells.