Volume 64, Issue 24 e202502215
Research Article

Regiospecific Halogenation Modulates Molecular Dipoles in Self-Assembled Monolayers for High-Performance Organic Solar Cells

Wenlin Jiang

Wenlin Jiang

Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, 999077 Hong Kong SAR

Both authors equally contributed to this work.

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Yanxun Li

Yanxun Li

Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, 999077 Hong Kong SAR

Shandong Key Laboratory of Intelligent Energy Materials, School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580 China

Both authors equally contributed to this work.

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Huanhuan Gao

Corresponding Author

Huanhuan Gao

Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, 999077 Hong Kong SAR

School of Materials Science and Engineering, Shandong University of Technology, Zibo, Shandong, 255000 China

E-mail: [email protected]; [email protected]

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Lingchen Kong

Lingchen Kong

Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, 999077 Hong Kong SAR

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Chun-To Wong

Chun-To Wong

Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, 999077 Hong Kong SAR

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Xi Yang

Xi Yang

Guangzhou Chasinglight Technology Co., Ltd, Guangzhou, Guangdong, 510535 China

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Francis R. Lin

Francis R. Lin

Department of Chemistry, City University of Hong Kong, Kowloon, 999077 Hong Kong SAR

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Alex K.-Y. Jen

Corresponding Author

Alex K.-Y. Jen

Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, 999077 Hong Kong SAR

Department of Chemistry, City University of Hong Kong, Kowloon, 999077 Hong Kong SAR

Hong Kong Institute for Clean Energy, City University of Hong Kong, Kowloon, 999077 Hong Kong SAR

State Key Laboratory of Marine Pollution, City University of Hong Kong, Kowloon, 999077 Hong Kong SAR

E-mail: [email protected]; [email protected]

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First published: 09 April 2025

Graphical Abstract

Herein, through regiospecific bromination on a helical 7H-dibenzo[c,g]carbazole-based SAM (CbzNaph) featuring a stronger dipole, we study the properties related to intrinsic stability, electrostatic potential (ESP) distribution, and changes in the molecular dipole of the derived SAM molecules. Bromination at the chemically inert sites of 7H-dibenzo[c,g]carbazole (JJ26) helps maximize molecular dipole while maintaining superior intrinsic stability. Together with the dense assembly promoted by enhanced intermolecular interactions and synergistic effects of stronger crystallinity, JJ26 efficiently modulates the work function (WF) of indium tin oxide (ITO) and enhances the stability of SAM under external pressure. The OSC device adopting JJ26 demonstrates significantly improved performance, achieving an efficiency of 19.35% along with notably enhanced stability.

Abstract

Halogenated carbazole-derived self-assembled monolayers (SAMs) are promising hole-extraction materials in conventional organic solar cells (OSCs). While halogenation helps optimize the molecular dipole, intermolecular interactions, and energetics of SAM, the highly polarizable carbon-halogen bonds can be reactive and prone to photocleavage depending on their regiochemistry. Herein, we study the regiospecific properties, including the intrinsic stability, electrostatic potential (ESP) distribution, and changes in molecular dipole of the brominated SAM molecules by brominating a helical 7H-dibenzo[c,g]carbazole-based SAM (CbzNaph) featuring a stronger dipole. Additionally, a correlation between the intrinsic molecular stability and the derived SAM surface stability is established to determine the performance and stability of the OSCs. Notably, the bromination at the chemically inert sites of 7H-dibenzo[c,g]carbazole (JJ26) helps maximize molecular dipole while maintaining superior intrinsic stability. Together with dense assembly promoted by the synergistically enhanced intermolecular interactions and crystallinity, JJ26 can efficiently modulate the work function (WF) of indium tin oxide (ITO) and enhance the stability of SAM under external stress. Consequently, the JJ26 derived OSC shows significantly improved performance, achieving an efficiency of 19.35% along with notably enhanced stability. This work shows that the precise modulation of the regiochemistry of SAM molecules is critical for improving their quality and derived device performance.

Conflict of Interests

The authors declare no conflict of interest.

Data Availability Statement

The data that support the findings of this study are available in the of this article.

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