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Exciton Binding Energies of Nonfullerene Small Molecule Acceptors: Implication for Exciton Dissociation Driving Forces in Organic Solar Cells
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2018-09-24 , DOI: 10.1021/acs.jpcc.8b07197
Lingyun Zhu 1 , Yuanping Yi 2 , Zhixiang Wei 1
Affiliation  

Reducing the driving force of exciton dissociation into charge-transfer states is one effective solution to minimize energy loss and thus to improve power conversion efficiencies for organic solar cells. Traditionally, the driving force should be larger than 0.3 eV to achieve efficient exciton dissociation. Recent experiments have shown that excitons can be effectively dissociated, whereas the energy offsets between donor and acceptor are extremely small, but the mechanisms are not understood yet. Here, we use system-optimized long-range corrected functional with solid-state electronic polarization to investigate exciton binding energies of 14 typical nonfullerene small molecule acceptors in organic solar cells. The results point to that the driving forces for dissociation of the acceptor excitons into charge-transfer states are linearly correlated to the exciton binding energies. The smaller the exciton binding energy, the lower driving force required. Moreover, primarily owing to the largest dielectric constants, IDT- or IDTT-based fused-ring acceptors have the smallest exciton binding energies with respect to other acceptors, i.e., DPP-, PDI-, and BFI-based systems. The influence of conjugation lengths, strengths of electron-donating and withdrawing units, and molecular volumes on the dielectric constants are analyzed in detail. Our work rationalizes the experimental observations and would be helpful for designing active materials to reduce energy loss for organic solar cells.

中文翻译:

非富勒烯小分子受体的激子结合能:激子解离驱动力在有机太阳能电池中的含义。

将激子离解的驱动力降低到电荷转移状态是一种有效的解决方案,可将能量损失降至最低,从而提高有机太阳能电池的功率转换效率。传统上,驱动力应大于0.3 eV,以实现有效的激子离解。最近的实验表明,激子可以有效地解离,而供体和受体之间的能量偏移非常小,但机理尚不清楚。在这里,我们使用具有固态电子极化的系统优化的远程校正功能来研究有机太阳能电池中14种典型的非富勒烯小分子受体的激子结合能。结果表明,受体激子解离成电荷转移态的驱动力与激子结合能线性相关。激子结合能越小,所需的驱动力越低。此外,主要由于最大的介电常数,基于IDT或IDTT的稠环受体相对于基于DPP,PDI和BFI的其他受体具有最小的激子结合能。详细分析了共轭长度,给电子和吸电子单元的强度以及分子体积对介电常数的影响。我们的工作合理化了实验观察结果,将有助于设计活性材料以减少有机太阳能电池的能量损失。所需的较低驱动力。此外,主要由于最大的介电常数,基于IDT或IDTT的稠环受体相对于基于DPP,PDI和BFI的其他受体具有最小的激子结合能。详细分析了共轭长度,给电子和吸电子单元的强度以及分子体积对介电常数的影响。我们的工作合理化了实验观察结果,将有助于设计活性材料以减少有机太阳能电池的能量损失。所需的较低驱动力。此外,主要由于最大的介电常数,基于IDT或IDTT的稠环受体相对于基于DPP,PDI和BFI的其他受体具有最小的激子结合能。详细分析了共轭长度,给电子和吸电子单元的强度以及分子体积对介电常数的影响。我们的工作合理化了实验观察结果,将有助于设计活性材料以减少有机太阳能电池的能量损失。给电子和吸电子单元的强度,以及分子体积对介电常数的详细分析。我们的工作合理化了实验观察结果,将有助于设计活性材料以减少有机太阳能电池的能量损失。给电子和吸电子单元的强度,以及分子体积对介电常数的详细分析。我们的工作合理化了实验观察结果,将有助于设计活性材料以减少有机太阳能电池的能量损失。
更新日期:2018-09-25
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