Increased Exciton Delocalization of Polymer upon Blending with Fullerene,Advanced Materials

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Increased Exciton Delocalization of Polymer upon Blending with Fullerene
Advanced Materials ( IF 27.4 ) Pub Date : 2018-06-11 , DOI: 10.1002/adma.201801392
Bhoj Gautam ₁ , Erik Klump ₂ , Xueping Yi ₂ , Iordania Constantinou ₂ , Nathan Shewmon ₂ , Amin Salehi ₁ , Chi Kin Lo ₃ , Zilong Zheng ₃ , Jean-Luc Brédas ₃ , Kenan Gundogdu ₁ , John R. Reynolds ₃ , Franky So ₂

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Interfaces between donor and acceptor in a polymer solar cell play a crucial role in exciton dissociation and charge photogeneration. While the importance of charge transfer (CT) excitons for free carrier generation is intensively studied, the effect of blending on the nature of the polymer excitons in relation to the blend nanomorphology remains largely unexplored. In this work, electroabsorption (EA) spectroscopy is used to study the excited‐state polarizability of polymer excitons in several polymer:fullerene blend systems, and it is found that excited‐state polarizability of polymer excitons in the blends is a strong function of blend nanomorphology. The increase in excited‐state polarizability with decreased domain size indicates that intermixing of states at the interface between the donor polymers and fullerene increases the exciton delocalization, resulting in an increase in exciton dissociation efficiency. This conclusion is further supported by transient absorption spectroscopy and time‐resolved photoluminescence measurements, along with the results from time‐dependent density functional theory calculations. These findings indicate that polymer excited‐state polarizability is a key parameter for efficient free carrier generation and should be considered in the design and development of high‐performance polymer solar cells.

中文翻译：

与富勒烯共混时，聚合物的激子离域增加

聚合物太阳能电池中供体和受体之间的界面在激子离解和电荷光生作用中起着至关重要的作用。尽管深入研究了电荷转移（CT）激子对产生自由载流子的重要性，但相对于共混物纳米形态而言，共混对聚合物激子性质的影响尚待进一步研究。在这项工作中，使用电吸收（EA）光谱研究了几种聚合物：富勒烯共混体系中聚合物激子的激发态极化率，发现共混物中聚合物激子的激发态极化率是共混物的强大功能。纳米形态。激发态极化率的增加与畴尺寸的减小表明，在供体聚合物和富勒烯之间的界面处的状态混合增加了激子离域化，从而导致了激子离解效率的提高。瞬态吸收光谱法和时间分辨的光致发光测量以及随时间变化的密度泛函理论计算的结果进一步支持了该结论。这些发现表明，聚合物激发态的极化率是有效产生自由载流子的关键参数，在高性能聚合物太阳能电池的设计和开发中应予以考虑。瞬态吸收光谱法和时间分辨的光致发光测量以及随时间变化的密度泛函理论计算的结果进一步支持了该结论。这些发现表明，聚合物激发态的极化率是有效产生自由载流子的关键参数，在高性能聚合物太阳能电池的设计和开发中应予以考虑。瞬态吸收光谱法和时间分辨的光致发光测量以及随时间变化的密度泛函理论计算的结果进一步支持了该结论。这些发现表明，聚合物激发态的极化率是有效产生自由载流子的关键参数，在高性能聚合物太阳能电池的设计和开发中应予以考虑。

更新日期：2018-06-11

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