Interfacial layer with a dibenzofulvene-bridged triphenylamine core for efficient and stable inverted perovskite solar cells

Considering the energy level cascade, introducing a hole transport layer (HTL) between the NiOx and perovskite layers has become a common and effective strategy to enhance the performance of inverted perovskite solar cells (PSCs). Herein, we designed and synthesized three hole-transporting interfacial layers (TPAD, TPAO, and TPAS) based on a dibenzofulvene-bridged triphenylamine (TPA) core to fabricate efficient and stable inverted NiOxbased PSCs. Dibenzofulvene, known for its sp2-hybridized structure, offers superior planarity and molecular stacking, and it easily bonds with triphenylamine derivatives, resulting in unique light-harvesting and charge mobility properties for optoelectronic applications. Specifically, diphenylamine, dimethoxy diphenylamine, and dimethylthio diphenylamine were used as end-capping units for TPAD, TPAO, and TPAS, respectively. The NiOxbased inverted PSC devices fabricated with TPAS as an interfacial layer effectively modified NiOx to improve energy level alignment, enhance film quality and crystallinity, and improve carrier transport, leading to a highquality perovskite layer and superior interface contact behavior. Consequently, this device yielded a highly efficient cell performance of 20.30 %, surpassing those using TPAD (19.29 %) and TPAO (18.78 %) as interfacial layers, and significantly outperforming devices using only NiOx (17.69 %). Additionally, the champion cell exhibited negligible hysteresis and long-term stability. These findings demonstrate a facile approach to preparing multifunctional TPA-based hole transport materials and showcase the efficient performance of inverted cells based on a triphenylamine dibenzofulvene-based interfacial layer, contributing to the development of highefficiency inverted PSCs.