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Vol. 19 (2027)

Layered Defect-Filling co-Assembled Carbazole-Based SAMs Deliver 20% Organic Solar Cells and 17% Mini-Modules

https://doi.org/10.1007/s40820-026-02325-2
Jingnan Wu
Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Göteborg, Sweden
Fengbo Sun
Key Laboratory of Special Functional Aggregated Materials (Shandong University), Ministry of Education, School of Chemistry & Chemical Engineering, National Engineering Research Center for Colloidal Materials, Shandong University, Jinan 250100, People’s Republic of China
Leandro R. Franco
Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Göteborg, Sweden
Qiaonan Chen
Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Göteborg, Sweden
Xinxin Xia
Key Laboratory of Special Functional Aggregated Materials (Shandong University), Ministry of Education, School of Chemistry & Chemical Engineering, National Engineering Research Center for Colloidal Materials, Shandong University, Jinan 250100, People’s Republic of China
Ruike Zhou
Key Laboratory of Flexible Optoelectronic Materials and Technology (Ministry of Education), School of Optoelectronic Materials & Technology, Jianghan University, Wuhan 430056, People’s Republic of China
Zhuang Li
Key Laboratory of Flexible Optoelectronic Materials and Technology (Ministry of Education), School of Optoelectronic Materials & Technology, Jianghan University, Wuhan 430056, People’s Republic of China
Mateus Bergami
Department of Engineering and Physics, Karlstad University, 651 88 Karlstad, Sweden
Pablo Hermosilla Fernandez
Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Göteborg, Sweden
C. Moyses Araujo
Department of Engineering and Physics, Karlstad University, 651 88 Karlstad, Sweden
Biao Xiao
Key Laboratory of Flexible Optoelectronic Materials and Technology (Ministry of Education), School of Optoelectronic Materials & Technology, Jianghan University, Wuhan 430056, People’s Republic of China
Xunchang Wang
Key Laboratory of Flexible Optoelectronic Materials and Technology (Ministry of Education), School of Optoelectronic Materials & Technology, Jianghan University, Wuhan 430056, People’s Republic of China
Donghong Yu
Department of Chemistry and Bioscience, Aalborg University, 9220 Aalborg, Denmark
Maojie Zhang
Key Laboratory of Special Functional Aggregated Materials (Shandong University), Ministry of Education, School of Chemistry & Chemical Engineering, National Engineering Research Center for Colloidal Materials, Shandong University, Jinan 250100, People’s Republic of China
Renqiang Yang
Key Laboratory of Flexible Optoelectronic Materials and Technology (Ministry of Education), School of Optoelectronic Materials & Technology, Jianghan University, Wuhan 430056, People’s Republic of China
Ergang Wang
Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Göteborg, Sweden

Corresponding Author: Ergang Wang

ergang@chalmers.se

Nano-Micro Letters, Vol. 19 (2027), Article Number: 29

Abstract

Self-assembled monolayers (SAMs) are widely used as hole-transport layers (HTLs) in organic solar cells (OSCs), yet conventional single-component SAMs often form quasi-monolayers with incomplete coverage and interfacial defects that become increasingly detrimental upon device scaling. Here, we develop a co-assembled multilayered SAM (coSAMu) strategy that combines two SAM molecules, 2PACz and 2Cl-4PACz, with distinct dipoles and steric configurations through blend casting and sequential casting. Photoelectron spectroscopy, X-ray analysis, and molecular simulations support a layered structure in which a chemisorbed, 2PACz-rich bottom layer primarily sets the indium tin oxide (ITO) work function, while a 2Cl-4PACz-rich upper layer fills interfacial voids, improves molecular packing, and passivates defects. Consistent with this picture, coSAMu promotes a more favorable vertical composition near the ITO surface and suppresses trap-assisted recombination, enabling more efficient charge extraction and collection. Consequently, a representative D18:L8-BO OSC incorporating the sequential-cast coSAMu HTL achieves a power conversion efficiency of 20.1% (0.042 cm2), outperforming pristine 2PACz. Importantly, when scaled to a 17.14 cm2 mini-module (six serially connected subcells), coSAMu delivers 17.0% efficiency versus 12.2% for the 2PACz control. This work demonstrates controlled multilayer co-assembly as an effective strategy for scalable OSC interface engineering that is broadly applicable to multiple donor–acceptor systems.


Highlights:
1 A sequential co-assembly of 2PACz and 2Cl-4PACz forms densely packed, electronically coupled SAM-based hole-transport layers.
2 The bottom 2PACz-rich monolayer tunes the indium tin oxide work function, while the upper 2Cl-4PACz layer fills interfacial voids, enhances packing, improves coupling with donor polymers, and promotes favorable vertical phase separation.
3 This cooperative interface engineering boosts charge transport and suppresses recombination, enabling organic solar cells to achieve a 20.1% power conversion efficiency and 17.0% mini-modules.

Keywords

Organic solar cells Interface engineering Self-assembled monolayers Trap passivation Scalable photovoltaics
Wu, Jingnan, Fengbo Sun, Leandro R. Franco, Qiaonan Chen, Xinxin Xia, Ruike Zhou, Zhuang Li, Mateus Bergami, Pablo Hermosilla Fernandez, C. Moyses Araujo, Biao Xiao, Xunchang Wang, Donghong Yu, Maojie Zhang, Renqiang Yang, and Ergang Wang. 2026. “Layered Defect-Filling Co-Assembled Carbazole-Based SAMs Deliver 20% Organic Solar Cells and 17% Mini-Modules”. Nano-Micro Letters 19 (August):29. https://doi.org/10.1007/s40820-026-02325-2.
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