Surface Passivation of Perovskite by Hole-Blocking Layer toward Efficient and Stable Inverted Solar Cells

Inverted (p-i-n) perovskite solar cells (PSCs) are advantageous in terms of easy fabrication, low-temperature processibility, negligible hysteresis, and excellent compatibility with the tandem devices in comparison with the regular (n-i-p) counterparts. Hole-blocking layer is crucial for efficient electron transport of inverted PSCs, and only a single hole-blocking layer of bathocuproine (BCP) is used typically. Herein, bis[2-(diphenylphosphino)phenyl] ether oxide (DPEPO) with a deep highest occupied molecular orbital (HOMO) energy level is incorporated atop of perovskite film as an auxiliary hole-blocking layer, resulting in an enhanced electron transport of inverted PSC devices. The P=O group within DPEPO can coordinate with Pb2+ cations of perovskite, leading to passivation of surface defects of perovskite. Besides, incorporation of DPEPO hole-blocking layer prohibits undesired hole transport from perovskite to PCBM electron transport layer (ETL), thus suppressing non-radiative electron-hole recombination. As a result, combined with BCP hole-blocking layer, inverted PSC devices based on double hole-blocking layers exhibit a decent power conversion efficiency (PCE) of 24.17% with a high open-circuit voltage (Voc) of 1.15 V which dramatically surpasses that based on single hole-blocking layer (22.26%). Moreover, incorporation of hydrophobic DPEPO helps to improve the ambient and thermal stabilities of inverted PSC devices. Bis[2-(diphenyl phosphate) phenyl] ether oxide (DPEPO) is incorporated as the interfacial passivation material of the perovskite/electron transport layer (ETL). Through the coordination interactions between the P=O group in DPEPO and the undercoordinated Pb2+, the defects in perovskite crystals are effectively eliminated, the interface non-radiative recombination is reduced, and the electron transport from perovskite to the ETL is promoted. Incorporation of DPEPO passivation layer leads to increased PCE of perovskite solar cell (PSC) from 22.26% to 24.17%.image (c) 2024 WILEY-VCH GmbH