Self-Assembled Monolayer Hole Transport Layers for High-Performance and Stable Inverted Perovskite Solar Cells

Abstract

NiOx is regarded as a kind of promising hole transport material in inverted perovskite solar cells (PSCs); however, the uncontrolled defects and unfavorable reactions within the perovskite layer go against device stability and power conversion efficiency (PCE). The pristine NiOx hole transport layer (HTL)-based PSCs usually require additional doping or interface engineering, which tends to introduce additional defects/sharp interfaces and thus affect the device performance. In this study, MeO-2PACz, a type of self-assembled materials (SAMs), was chosen to replace the standard NiOx as HTL and employed in inverted PSCs, since it possesses the potential for manufacturing high-performance stable PSCs. The results demonstrated that MeO-2PACz interacts with uncoordinated Pb2+ in the perovskite film, effectively passivating buried interface defects. Besides, the perovskite film deposited on MeO-2PACz HTL has improved crystallization quality and abated grain boundaries. Meanwhile, the good band alignment of the MeO-2PACz HTL/perovskite interface minimizes nonradiative recombination loss at the interface, considerably boosting charge extraction/transport efficiency and device performance. Accordingly, the device based on MeO-2PACz HTL achieved a champion PCE of 21.61% with a fill factor (FF) of 82.30%, accompanied by good stability, maintaining 94.0% of its initial PCE after 3000 h storage in ambient air without encapsulation at 25 °C. Hopefully, this work presents a novel approach to overcome the shortcomings of NiOx HTL-based PSCs, guaranteeing better performance.