Charge Generation via Relaxed Charge-Transfer States in Organic Photovoltaics by an Energy-Disorder-Driven Entropy Gain

Y. Puttisong, Y. Xia, X. Chen, F. Gao, I. A. Buyanova, O. Inganäs, W. M. Chen

研究成果: ジャーナルへの寄稿学術誌査読

19 被引用数 (Scopus)

抄録

In organic photovoltaics, efficient charge generation relies on our ability to convert excitons into free charges. Efficient charge separation from "energetic excitons" has been understood to be governed by delocalization effects promoted by molecular aggregation. A remaining puzzle is, however, the mechanism underlying charge generation via relaxed interfacial charge-transfer (CT) excitons that also exhibit an internal quantum efficiency close to unity. Here, we provide evidence for efficient charge generation via CT state absorption over a temperature range of 50-300 K, despite an intrinsically strong Coulomb binding energy of about 400 meV that cannot be modified by fullerene aggregation. We explain our observation by entropy-driven charge separation, with a key contribution from energy disorder. The energy disorder reduces the charge generation barrier by substantially gaining the entropy as electron-hole distance increases, resulting in efficient CT exciton dissociation. Our results underline an emerging consideration of energy disorder in thermodynamic stability of charge pairs and highlight the energy disorder as a dominant factor for generating charges via the CT state. A discussion for a trade-off in harvesting charges from relaxed CT excitons is also provided.

本文言語英語
ページ(範囲)12643-12646
ページ数4
ジャーナルJournal of Physical Chemistry C
122
24
DOI
出版ステータス出版済み - 6月 21 2018
外部発表はい

!!!All Science Journal Classification (ASJC) codes

  • 電子材料、光学材料、および磁性材料
  • エネルギー(全般)
  • 物理化学および理論化学
  • 表面、皮膜および薄膜

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