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<p>Designing active layer materials with high dielectric constants (<i>ε</i><sub>r</sub>) and low exciton binding energy (<i>E</i><sub>b</sub>) has emerged as an effective approach to improve the performance of organic solar cells (OSCs), yet there is a lack of clear molecular design strategies. In this study, a dipole-asymmetric molecule, AA-4, is designed and synthesized by adjusting the thiophene units on each side of the conjugated backbone and simultaneously incorporating electron-rich alkoxy side chains. Compared to its symmetric counterpart BO-4F, AA-4 achieves a higher <i>ε</i><sub>r</sub> and a markedly lower <i>E</i><sub>b</sub>, which together facilitate more efficient exciton dissociation and charge separation in the active layer. These improvements can be attributed to its dipole-asymmetric backbone and the introduction of electron-rich alkoxy side chains, which also influence intermolecular interactions. As a result, AA-4 exhibits tighter molecular packing, improved charge carrier mobility and suppressed energetic disorder, all of which synergistically contribute to enhanced device performance. Thus, the AA-4-based binary OSCs achieve a high fill factor of over 81%. Moreover, the favorable interfacial interaction and morphology of AA-4 enable the ternary device to achieve a high efficiency of 20.0%. This work provides new insights into the design of asymmetric-dipole materials with high dielectric constants for high-performance OSCs.</p>

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Reduced exciton binding energy via designing dipole-asymmetric acceptors for efficient organic solar cells

  • 期刊论文

  • 发表日期：

    2026年4月14日

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  • Haoyu Yuan,
  • Yang Xiao,
  • Jiana Zheng,
  • Runnan Yu,
  • Zhihao Chen,
  • Wenye Xu,
  • Jiawei Qiao,
  • Xiaotao Hao,
  • Jianhui Hou,
  • Yong Cui

摘要

Designing active layer materials with high dielectric constants (εr) and low exciton binding energy (Eb) has emerged as an effective approach to improve the performance of organic solar cells (OSCs), yet there is a lack of clear molecular design strategies. In this study, a dipole-asymmetric molecule, AA-4, is designed and synthesized by adjusting the thiophene units on each side of the conjugated backbone and simultaneously incorporating electron-rich alkoxy side chains. Compared to its symmetric counterpart BO-4F, AA-4 achieves a higher εr and a markedly lower Eb, which together facilitate more efficient exciton dissociation and charge separation in the active layer. These improvements can be attributed to its dipole-asymmetric backbone and the introduction of electron-rich alkoxy side chains, which also influence intermolecular interactions. As a result, AA-4 exhibits tighter molecular packing, improved charge carrier mobility and suppressed energetic disorder, all of which synergistically contribute to enhanced device performance. Thus, the AA-4-based binary OSCs achieve a high fill factor of over 81%. Moreover, the favorable interfacial interaction and morphology of AA-4 enable the ternary device to achieve a high efficiency of 20.0%. This work provides new insights into the design of asymmetric-dipole materials with high dielectric constants for high-performance OSCs.