Constructing Stable Perovskite with Small Molecule Bridge Interface Passivation

The interfaces of each layer in perovskite solar cells (PSCs) have a significant impact on the charge transfer and recombination. Especially, the interface between perovskite and the hole transport layer (HTL) in p-i-n type PSCs significantly affects the contact characteristics between the HTL and perovskite, hindering further improvements in performance and stability. Herein, a small molecule 9-Fluorenylmethoxycarbonyl chloride (9-YT) is introduced as a molecule bridge for p-i-n PSCs, which enhances the interaction between self-assembly molecules (SAMs) and perovskite. The conjugated backbone of 9-YT can interact with the SAM molecule (MeO-2PACz) by π–π stacking reaction. Moreover, 9-YT also improves the interfacial contact through strong interactions with the perovskite, where the carbonyl groups and Cl atoms in 9-YT interact with uncoordinated Pb²⁺ in perovskite layer. The incorporation of a molecule bridge is demonstrated to markedly enhance hole extraction at the perovskite/hole transport layer interface, optimize energy level alignment, mitigate interface charge recombination, and passivate the uncoordinated Pb²⁺ and defects in the perovskite. Finally, the device treated with 9-YT achieves a power conversion efficiency (PCE) of 24.82%. At the same time, PSCs can still maintain 92.6% of the original PCE after a long-term stability test of 1200 h.