Self-Assembled Monolayer Suppresses Interfacial Reaction between NiO_x and Perovskite for Efficient and Stable Inverted Inorganic Perovskite Solar Cells

Abstract

Inorganic NiO x has attracted tremendous attention in organic−inorganic hybrid perovskite solar cells (PSCs) in recent years but is relatively less used in all-inorganic PSCs. In this study, we have discovered and confirmed the detrimental interfacial reaction between NiO x and DMAI-containing CsPbI 3 inorganic perovskites. Thus, a self-assembled monolayer, Br-2PACz, is employed to modify the NiO x surface to obstruct the adverse interfacial reaction and further improve the device performance. The results demonstrate that Br-2PACz modification on NiO x can also improve interface contact, perovskite film morphology, and energy level alignments. Consequently, a champion power conversion efficiency (PCE) of 19.34% with a high open-circuit voltage (V OC ) of 1.15 V is obtained for inverted NiO x /Br-2PACz-based CsPbI 3 PSCs compared to the reference NiO x -based PSC with a moderate PCE of 15.16% (V OC 1.05 V). Moreover, the stabilities of both CsPbI 3 films and devices exhibited significant enhancement after Br-2PACz modification. The unpacked PSCs could maintain 80, 73, and 89% of the initial efficiency after aging in 30− 35% RH for 960 h, heating at 60 °C for 48 h, and continuous illumination for 284 h, respectively, highly superior to the reference devices. Our work offers a facile and effective approach for developing high-performance inverted NiO x -based CsPbI 3 PSCs.