Transient Dipole Strategy Boosts Highly Oriented Self-Assembled Monolayers for Organic Solar Cells Approaching 21% Efficiency
Hongyu Mou1, Yue Yin1, Haiyang Chen1（陈海阳）*, Jiacheng Xu1, Junyuan Ding1, Chen Ju1, Juan Zhu1, Yingyi Wang1, Weijie Chen1, Guiying Xu1, Tianjiao Zhang1, Jia Li1, Yaowen Li1（李耀文）*, Yongfang Li1,2,3
1Laboratory of Advanced Optoelectronic Materials, Suzhou Key Laboratory of Novel Semiconductor-optoelectronics Materials and Devices, State Key Laboratory of Bioinspired Interfacial Materials Science, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China
2Jiangsu Key Laboratory of Advanced Negative Carbon Technologies, Soochow University, Suzhou 215123, China
3Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
J. Am. Chem. Soc. 2025, 147, 21241
Abstract: Self-assembled monolayers (SAMs) based on carbazole with minimal parasitic absorption, such as the most widely used [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz), dominate the high-performance hole transport layer (HTL) for conventional organic solar cells (OSCs). However, the small dipole moment of the 2PACz molecules results in weak molecular dipole–dipole interactions, leading to disordered dipole orientation and restricting work function modulation, which causes serious interfacial energy loss. Here, we grafted thiophene groups at both ends of the carbazole in 2PACz to obtain an SAM material (Th-Cz), which formed a transient resonance structure during thermal annealing, resulting in a twice-enlarged dipole moment. This strengthened molecular dipole–dipole interactions, facilitating ordered arrangement and dipole orientation of the Th-Cz film, contributing to a higher work function, which enhanced hole extraction and suppressed energy losses at the SAM/active layer interface. Additionally, van der Waals interactions between Th-Cz and the donors enabled the donor crystallizing before the acceptor, and this phenomenon is different from the cocrystallization observed in 2PACz-based active layers. This manipulation of crystallization dynamics favors vertical phase separation with a donor-rich phase at the bottom of active layers, leading to balanced charge-carrier mobilities. The resultant OSCs based on PM6:Y6 and D18-Cl:N3:AT-β2O with Th-Cz as HTL achieved power conversion efficiencies (PCEs) of 19.34% and 20.91% (certified 20.67%), respectively, setting a record PCE for the PM6:Y6-based OSCs and achieving the highest certified PCE for single-junction OSCs to date. Notably, Th-Cz also demonstrated exceptional compatibility with flexible OSCs, delivering a record PCE of 19.63%.
Article information: //doi.org/10.1021/jacs.5c08124
