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.
Researchers from South China University of Technology and Guangxi University have introduced a small molecule 9-Fluorenylmethoxycarbonyl chloride (9-YT) 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 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.
