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Two-step crystallization modulated through acenaphthene enabling 21% binary organic solar cells and 83.2% fill factor

Nature Energy (2025)Cite this article

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Abstract

The crystallization dynamics of non-fullerene acceptors influences the morphology and charge dynamics of the resulting organic solar cells, ultimately determining device performance. However, optimizing the molecular arrangement of donor and acceptor materials within the active layer remains challenging. Here we control the crystallization kinetics of non-fullerene acceptors with a crystallization-regulating agent, acenaphthene. Acenaphthene changes the self-organization of acceptor molecules by inducing a two-step crystallization: it first fixes the packing motif of the acceptor and then refines the crystallized framework, leading to highly oriented acceptors in the active layer. This forms several charge-transport pathways that improve the charge-transport properties of the device. As a result, efficiencies of 20.9% (20.4% certified) and 21% (20.5% certified) are achieved in D18/L8-BO and PM1/L8-BO-X binary organic solar cells, respectively, with a maximum fill factor of 83.2% (82.2% certified). The result is a step forward in the development of organic solar cells.

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Fig. 1: Chemical structures and device performance.
Fig. 2: Charge-carrier dynamics.
Fig. 3: Crystalline packing motifs.
Fig. 4: In situ UV–vis characterization.
Fig. 5: In situ GIWAXS characterizations.
Fig. 6: Interactions between AP and NFA molecules and performance of the best device.

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Data availability

The data that support the findings of this study are available within the Article and its Supplementary Information. Source data are provided with this paper.

References

  1. Lin, Y. et al. An electron acceptor challenging fullerenes for efficient polymer solar cells. Adv. Mater. 27, 1170–1174 (2015).

    Article  Google Scholar 

  2. Yuan, J. et al. Enabling low voltage losses and high photocurrent in fullerene-free organic photovoltaics. Nat. Commun. 10, 570 (2019).

    Article  Google Scholar 

  3. Yuan, J. et al. Single-junction organic solar cell with over 15% efficiency using fused-ring acceptor with electron-deficient core. Joule 3, 1140–1151 (2019).

    Article  Google Scholar 

  4. Zhang, M., Guo, X., Ma, W., Ade, H. & Hou, J. A large‐bandgap conjugated polymer for versatile photovoltaic applications with high performance. Adv. Mater. 27, 4655–4660 (2015).

    Article  Google Scholar 

  5. Sun, C. et al. A low cost and high performance polymer donor material for polymer solar cells. Nat. Commun. 9, 743 (2018).

    Article  Google Scholar 

  6. Liu, Q. et al. 18% efficiency organic solar cells. Sci. Bull. 65, 272–275 (2020).

    Article  Google Scholar 

  7. Fu, J. et al. Rational molecular and device design enables organic solar cells approaching 20% efficiency. Nat. Commun. 15, 1830 (2024).

    Article  Google Scholar 

  8. Sun, K. et al. The role of solvent vapor annealing in highly efficient air-processed small molecule solar cells. J. Mater. Chem. A 2, 9048–9054 (2014).

    Article  Google Scholar 

  9. Fu, J. et al. A ‘σ-hole’-containing volatile solid additive enabling 16.5% efficiency organic solar cells. iScience 23, 100965 (2020).

    Article  Google Scholar 

  10. McDowell, C., Abdelsamie, M., Toney, M. F. & Bazan, G. C. Solvent additives: key morphology-directing agents for solution-processed organic solar cells. Adv. Mater. 30, 1707114 (2018).

    Article  Google Scholar 

  11. Liu, H. et al. Dual‐additive‐driven morphology optimization for solvent‐annealing‐free all‐small‐molecule organic solar cells. Adv. Funct. Mater. 33, 2303307 (2023).

    Article  Google Scholar 

  12. Fu, J. et al. 19.31% binary organic solar cell and low non-radiative recombination enabled by non-monotonic intermediate state transition. Nat. Commun. 14, 1760 (2023).

    Article  Google Scholar 

  13. Liu, K. et al. 19.7% efficiency binary organic solar cells achieved by selective core fluorination of nonfullerene electron acceptors. Joule 8, 835–851 (2024).

    Article  Google Scholar 

  14. Wang, L. et al. Donor–acceptor mutually diluted heterojunctions for layer-by-layer fabrication of high-performance organic solar cells. Nat. Energy 9, 208–218 (2024).

    Article  Google Scholar 

  15. Tu, L. et al. Cyano-functionalized pyrazine: an electron-deficient unit as a solid additive enables binary organic solar cells with 19.67% efficiency. Energy Environ. Sci. 17, 3365–3374 (2024).

    Article  Google Scholar 

  16. Guan, S. et al. Self‐assembled interlayer enables high‐performance organic photovoltaics with power conversion efficiency exceeding 20%. Adv. Mater. 36, 2400342 (2024).

  17. Jiang, Y. et al. Non-fullerene acceptor with asymmetric structure and phenyl-substituted alkyl side chain for 20.2% efficiency organic solar cells. Nat. Energy 9, 975–986 (2024).

    Article  Google Scholar 

  18. Li, G. et al. High-efficiency solution processable polymer photovoltaic cells by self-organization of polymer blends. Nat. Mater. 4, 864–868 (2005).

    Article  Google Scholar 

  19. Qin, J. et al. 17% efficiency all-small-molecule organic solar cells enabled by nanoscale phase separation with a hierarchical branched structure. Energy Environ. Sci. 14, 5903–5910 (2021).

    Article  Google Scholar 

  20. Zhan, L. et al. Layer‐by‐layer processed ternary organic photovoltaics with efficiency over 18%. Adv. Mater. 33, 2007231 (2021).

    Article  Google Scholar 

  21. Zhang, Y. et al. Graded bulk-heterojunction enables 17% binary organic solar cells via nonhalogenated open air coating. Nat. Commun. 12, 4815 (2021).

    Article  Google Scholar 

  22. Qin, J. et al. Volatile solid additive‐assisted sequential deposition enables 18.42% efficiency in organic solar cells. Adv. Sci. 9, 2105347 (2022).

    Article  Google Scholar 

  23. Zhang, Y. et al. Achieving 19.4% organic solar cell via an in situ formation of pin structure with built-in interpenetrating network. Joule 8, 509–526 (2024).

    Article  Google Scholar 

  24. Wu, W. et al. Defining solid additive’s pivotal role on morphology regulation in organic solar cells produced by layer‐by‐layer deposition. Adv. Energy Mater. 14, 2400354 (2024).

  25. Lai, H. et al. Exploring the significance of packing modes and 3D framework sizes and utilizing three chlorine-mediated acceptors and the ‘like dissolves like’ approach for achieving an efficiency over 19. Energy Environ. Sci. 16, 5944–5955 (2023).

    Article  Google Scholar 

  26. Lai, H. et al. Crystallography, packing mode, and aggregation state of chlorinated isomers for efficient organic solar cells. CCS Chem. 5, 1118–1129 (2023).

    Article  Google Scholar 

  27. Fu, J. et al. Eutectic phase behavior induced by a simple additive contributes to efficient organic solar cells. Nano Energy 84, 105862 (2021).

    Article  Google Scholar 

  28. Gutierrez‐Fernandez, E. et al. Y6 organic thin‐film transistors with electron mobilities of 2.4 cm2 V−1 s−1 via microstructural tuning. Adv. Sci. 9, 2104977 (2022).

    Article  Google Scholar 

  29. Verploegen, E. et al. Effects of thermal annealing upon the morphology of polymer–fullerene blends. Adv. Funct. Mater. 20, 3519–3529 (2010).

    Article  Google Scholar 

  30. Cui, Y. et al. Single‐junction organic photovoltaic cells with approaching 18% efficiency. Adv. Mater. 32, 1908205 (2020).

    Article  Google Scholar 

  31. Sun, X. et al. Binary organic solar cells with >19.6% efficiency: the significance of self-assembled monolayer modification. ACS Energy Lett. 9, 4209–4217 (2024).

    Article  Google Scholar 

  32. Zhan, L. et al. Desired open-circuit voltage increase enables efficiencies approaching 19% in symmetric-asymmetric molecule ternary organic photovoltaics. Joule 6, 662–675 (2022).

    Article  Google Scholar 

  33. Qin, Y. et al. The performance-stability conundrum of BTP-based organic solar cells. Joule 5, 2129–2147 (2021).

    Article  Google Scholar 

  34. Chen, S. et al. Photo‐carrier recombination in polymer solar cells based on P3HT and silole‐based copolymer. Adv. Energy Mater. 1, 963–969 (2011).

    Article  Google Scholar 

  35. Zhao, Z. et al. Suppressing bimolecular charge recombination and energetic disorder with planar heterojunction active layer enables 18.1% efficiency binary organic solar cells. ACS Mater. Lett. 5, 1718–1726 (2023).

    Article  Google Scholar 

  36. Ni, Z. et al. Resolving spatial and energetic distributions of trap states in metal halide perovskite solar cells. Science 367, 1352–1358 (2020).

    Article  Google Scholar 

  37. Dela Peña, T. A. et al. Manipulating the charge carriers through functionally bridged components advances low‐cost organic solar cells with green solvent processing. Adv. Energy Mater. 14, 2303169 (2024).

    Article  Google Scholar 

  38. Peña, T. A. D. et al. Interface property–functionality interplay suppresses bimolecular recombination facilitating above 18% efficiency organic solar cells embracing simplistic fabrication. Energy Environ. Sci. 16, 3416–3429 (2023).

    Article  Google Scholar 

  39. Xia, X. et al. Revealing the crystalline packing structure of Y6 in the active layer of organic solar cells: the critical role of solvent additives. J. Mater. Chem. A 11, 21895–21907 (2023).

    Article  Google Scholar 

  40. Zhang, G. et al. Delocalization of exciton and electron wavefunction in non-fullerene acceptor molecules enables efficient organic solar cells. Nat. Commun. 11, 3943 (2020).

    Article  Google Scholar 

  41. Kupgan, G., Chen, X. & Bredas, J.-L. Molecular packing of non-fullerene acceptors for organic solar cells: distinctive local morphology in Y6 vs. ITIC derivatives. Mater. Today Adv. 11, 100154 (2021).

    Article  Google Scholar 

  42. Yuk, D. et al. Simplified Y6‐based nonfullerene acceptors: in‐depth study on molecular structure–property relation, molecular dynamics simulation, and charge dynamics. Small 19, 2206547 (2023).

    Article  Google Scholar 

  43. Cai, G. et al. Deuteration-enhanced neutron contrasts to probe amorphous domain sizes in organic photovoltaic bulk heterojunction films. Nat. Commun. 15, 2784 (2024).

    Article  Google Scholar 

  44. Lindon, J. C., Tranter, G. E. & Koppenaal, D. Encyclopedia of Spectroscopy and Spectrometry 3rd edn (Academic Press, 2016).

  45. Frisch, M. J. et al. Gaussian 16 (Gaussian, 2016).

  46. Bannwarth, C. et al. Extended tight‐binding quantum chemistry methods. Wiley Interdiscip. Rev.: Comput. Mol. Sci. 11, e1493 (2021).

    Google Scholar 

  47. Li, C. et al. Non-fullerene acceptors with branched side chains and improved molecular packing to exceed 18% efficiency in organic solar cells. Nat. Energy 6, 605–613 (2021).

    Article  Google Scholar 

  48. Cui, Y. et al. Organic photovoltaic cell with 17% efficiency and superior processability. Natl Sci. Rev. 7, 1239–1246 (2020).

    Article  Google Scholar 

  49. Wu, J. et al. Random terpolymer based on thiophene-thiazolothiazole unit enabling efficient non-fullerene organic solar cells. Nat. Commun. 11, 4612 (2020).

    Article  Google Scholar 

  50. Luo, S. et al. Auxiliary sequential deposition enables 19%-efficiency organic solar cells processed from halogen-free solvents. Nat. Commun. 14, 6964 (2023).

    Article  Google Scholar 

  51. Zhu, L. et al. Achieving 20.8% organic solar cells via additive-assisted layer-by-layer fabrication with bulk pin structure and improved optical management. Joule 8, 3153–3168 (2024).

    Article  Google Scholar 

  52. Yu, Y. et al. Naphthalene diimide-based cathode interlayer material enables 20.2% efficiency in organic photovoltaic cells. Sci. China Chem. 67, 4194–4201 (2024).

    Article  Google Scholar 

  53. Chen, Z. et al. 20.2% efficiency organic photovoltaics employing a π‐extension quinoxaline‐based acceptor with ordered arrangement. Adv. Mater. 36, 2406690 (2024).

    Article  Google Scholar 

  54. Chen, H. et al. Organic solar cells with 20.82% efficiency and high tolerance of active layer thickness through crystallization sequence manipulation. Nat. Mater. 24, 444–453 (2025).

    Article  Google Scholar 

  55. Chen, C. et al. Molecular interaction induced dual fibrils towards organic solar cells with certified efficiency over 20. Nat. Commun. 15, 6865 (2024).

    Article  Google Scholar 

  56. Li, C. et al. Highly efficient organic solar cells enabled by suppressing triplet exciton formation and non-radiative recombination. Nat. Commun. 15, 8872 (2024).

    Article  Google Scholar 

  57. Guan, S. et al. Fine-tuning the hierarchical morphology of multi-component organic photovoltaics via a dual-additive strategy for 20.5% efficiency. Energy Environ. Sci. 18, 313–321 (2025).

    Article  Google Scholar 

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Acknowledgements

G.L. thanks the Research Grants Council of Hong Kong (GRF Grant No. 15211320, CRF C4005-22Y and the RGC Senior Research Fellowship Scheme (SRFS2223-5S01)), Hong Kong Polytechnic University (the Sir Sze-yuen Chung Endowed Professorship Fund (8-8480), RISE (Q-CDBK), G-SAC5, PRI (1-CD7X)) and Guangdong-Hong Kong-Macao Joint Laboratory for Photonic-Thermal-Electrical Energy Materials and Devices (GDSTC No. 2019B121205001). H. Li thanks the Sichuan Science and Technology Programme (Grant No. 2023NSFSC0990). We thank Y. Chen (Beijing Synchrotron Radiation Facility) and L. Wang (Beijing Zhongke Wanyuan Technology) for the in situ spin-coating GIWAXS experiments. This work was carried out with the support of the SSRF, beamline BL02U2. We thank SSRF BL02U2 for the 2D GIWAXS measurements.

Author information

Author notes

  1. These authors contributed equally: Jiehao Fu, Hongxiang Li, Heng Liu.

Authors and Affiliations

  1. Department of Electrical and Electronic Engineering, Research Institute for Smart Energy (RISE), Photonic Research Institute (PRI), The Hong Kong Polytechnic University, Kowloon, Hong Kong, China

    Jiehao Fu, Patrick W. K. Fong & Gang Li

  2. College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, China

    Hongxiang Li & Pei Cheng

  3. Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong, China

    Heng Liu & Xinhui Lu

  4. Thin-film Solar Cell Technology Research Center, Chongqing Institute of Green and Intelligent Technology, Chongqing School, University of Chinese Academy of Sciences (UCAS Chongqing), Chinese Academy of Sciences, Chongqing, China

    Peihao Huang, Haiyan Chen & Zeyun Xiao

  5. Advanced Materials Thrust, Function Hub, The Hong Kong University of Science and Technology, Guangzhou, China

    Top Archie Dela Peña

  6. Department of Applied Physics, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China

    Mingjie Li

  7. Zhejiang Key Laboratory for Island Green Energy and New Materials, School of Materials Science and Engineering, Taizhou University, Taizhou, China

    Shirong Lu

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Contributions

J.F. and G.L. conceived the study. J.F. fabricated the devices and performed most of the characterizations and analysis. H. Li and P.C. performed the in situ GIWAXS measurements and analysis. H. Liu and X.L. performed the ex situ GISAXS measurements and analysis. P.H. performed the density functional theory calculations. H.C., Z.X. and S.L. assisted with the NMR measurements and analysis. P.W.K.F. conducted the in situ UV–vis characterization. G.L. guided the study and supervised the execution. The paper was prepared, revised and finalized by J.F., H. Li, H. Liu and G.L. All authors discussed the results and commented on the paper.

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Correspondence to Gang Li.

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Supplementary information

Supplementary Information

Supplementary Notes 1 and 2, Figs. 1–34 and Tables 1–6.

Reporting Summary

Supplementary Video 1

Time-resolved GIWAXS patterns of the control sample during spin-coating.

Supplementary Video 2

Time-resolved GIWAXS patterns of the AP sample during spin-coating.

Supplementary Video 3

Time-resolved GIWAXS patterns of the control sample during thermal annealing.

Supplementary Video 4

Time-resolved GIWAXS patterns of the AP sample during thermal annealing.

Supplementary Data

Source data for supplementary figures and tables.

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Source Data Fig. 1

Statistical source data for Fig. 1.

Source Data Fig. 6

Statistical source data for Fig. 6.

Source Data Table 1

Statistical source data for Table 1.

Source Data Table 2

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Fu, J., Li, H., Liu, H. et al. Two-step crystallization modulated through acenaphthene enabling 21% binary organic solar cells and 83.2% fill factor. Nat Energy (2025). https://doi.org/10.1038/s41560-025-01862-1

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