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Non-fullerene acceptor with asymmetric structure and phenyl-substituted alkyl side chain for 20.2% efficiency organic solar cells

Abstract

For organic solar cells (OSCs), bridging the gap with Shockley–Queisser limit necessitates simultaneously reducing the energy loss for a high open-circuit voltage, improving light utilization for enhanced short-circuit current density and maintaining ideal nanomorphology with a high fill factor through molecular design and device engineering. Here we design and synthesize an asymmetric non-fullerene acceptor (Z8) featuring tethered phenyl groups to establish an alloy acceptor in ternary OSCs. The asymmetric structure minimizes non-radiative energy loss and charge recombination owing to delocalized excitons. The phenyl-substituted alkyl side chain impacts on the intermolecular interactions, improving the film nanomorphology with efficient exciton dissociation and reduced charge recombination. We demonstrate OSCs with an efficiency of 20.2% (certified 19.8%) based on the D18:Z8:L8-BO ternary blend. Through theoretical calculations, we examine the overall distribution of photon and carrier losses and analyse the potential for improvement on open-circuit voltage, short-circuit current density and fill factor, providing rational guidance for further development of the OSC performance.

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Fig. 1: Materials and device performance.
Fig. 2: Charge dynamics analysis.
Fig. 3: Morphology characterizations.
Fig. 4: Theoretical evaluation.

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The authors declare all data supporting the findings of this study are available within the manuscript and Supplementary Information. Source data are provided with this paper.

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Acknowledgements

This work was supported by the Beijing Natural Science Foundation (Z230019), the National Key R&D Program of China (2019YFA0705900), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB0520202), the International Partnership Program of the Chinese Academy of Sciences (027GJHZ2022036GC) and National Natural Science Foundation of China (52225305, 22175187 and 22375119). The authors thank C. Zhu, L. Meng and Y. Li for their help with the TPC, TPV and CE measurements, and M. Xie and Z. Wei for their help with the FTPS-EQE and EQEEL measurements, and X. Pu for his help with photo-induced force microscopy measurement, and Y. Ouyang and C. Zhang for their help in TA measurements, and X. Chen, Q. Luo and C. Ma for their help in MMP measurements and Y. Fu and X. Lu for their help in GISAXS measurements.

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X.Z. and F.L. conceived the study. Y.J. and F.L. fabricated the solar cells and performed the related measurements. S.S. performed theoretical calculations. R.X. and K.L. synthesized the NFAs Z7 and Z8. G.R. and W.Z. performed the TA spectra analysis. X.Z. supervised the project. X.M. and Y.Y. performed MD simulation. The manuscript was mainly written by Y.J., S.S., F.L. and X.Z. All the authors contributed to the data analysis and discussion.

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Correspondence to Feng Liu or Xiaozhang Zhu.

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Nature Energy thanks Yanming Sun, Hin-Lap Yip and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Jiang, Y., Sun, S., Xu, R. et al. Non-fullerene acceptor with asymmetric structure and phenyl-substituted alkyl side chain for 20.2% efficiency organic solar cells. Nat Energy (2024). https://doi.org/10.1038/s41560-024-01557-z

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