揭示推拉型聚合物半导体中的多量子激子关联
Unveiling multi-quantum excitonic correlations in push-pull polymer semiconductors
AI总结：
本文利用相干二维光谱在推拉型聚合物半导体中识别出束缚与非束缚Frenkel激子复合体，通过双激子模型解释交叉峰不平衡，并揭示非束缚激子对中的多体相互作用。
摘要：
束缚和非束缚的Frenkel激子对是多种光物理和生物化学过程中必不可少的瞬态前驱体。在本工作中，我们利用相干二维光谱在一种电子推拉型聚合物半导体中识别出束缚和非束缚的Frenkel激子复合体。我们发现吸收振动级联的主导$A_{0-1}$峰伴随一个子峰，每个峰都由不同的振动模式修饰。通过在双激子模型中考虑Liouville路径，单量子重相和非重相光谱中的不平衡交叉峰可以由纯双激子的存在来解释。另一方面，双量子非重相光谱为非束缚激子对和以吸引力为主导的双激子提供了直接证据。此外，非束缚激子对的光谱特征表现出混合的吸收型和色散型特征，暗示关联Frenkel激子对内部存在多体相互作用。我们的工作为存在Frenkel激子复合体的半导体聚合物中丰富的光物理过程提供了新的视角。
英文摘要：
Bound and unbound Frenkel-exciton pairs are essential transient precursors for a variety of photophysical and biochemical processes. In this work, we identify bound and unbound {Frenkel}-exciton complexes in an electron push-pull polymer semiconductor using coherent two-dimensional spectroscopy. We find that the dominant $A_{0-1}$ peak of the absorption vibronic progression is accompanied by a sub-peak, each dressed by distinct vibrational modes. By considering the Liouville pathways within a two-exciton model, the imbalanced cross peaks in one-quantum rephasing and non-rephasing spectra can be accounted for by the presence of pure biexcitons. The two-quantum non-rephasing spectra, on the other hand, provide direct evidence for unbound exciton pairs and biexcitons with dominantly attractive force. In addition, the spectral features of unbound exciton pairs show mixed absorptive and dispersive character, implying many-body interactions within the correlated {Frenkel}-exciton pairs. Our work offers novel perspectives on the rich photophysical processes in semiconductor polymers with the presence of Frenkel exciton complexes.
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