Extracting Electrons from Delocalized Excitons by Flattening the Energetic Pathway for Charge Separation,The Journal of Physical Chemistry Letters

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Extracting Electrons from Delocalized Excitons by Flattening the Energetic Pathway for Charge Separation
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2021-09-13 , DOI: 10.1021/acs.jpclett.1c02228
Shanika Wanigasekara ₁ , Bhupal Kattel ₁ , Fatimah Rudayni ₁ , Wai-Lun Chan ₁

Affiliation

At organic donor–acceptor (D–A) interfaces, electron and hole are bound together to form charge transfer (CT) excitons. The electron and hole wave functions in these CT excitons can spatially delocalize. The electron delocalization opens up possibilities of extracting free charges from bound excitons by manipulating the potential energy landscape on the nanoscale. Using a prototype trilayer structure that has a cascade band structure, we show that the yield of charge separation can be doubled as compared to the bilayer counterpart when the thickness of the intermediate layer is around 3 nm. This thickness coincides with the electron delocalization size of CT excitons typically found in these organic films. Tight-binding calculation for the CT states in the trilayer structure further demonstrates that electron delocalization, together with the energy level cascade, can effectively flatten the energetic pathway for charge separation. Hence, it is possible to add nanometer-thick layers between the donor and the acceptor to significantly enhance the charge separation yield.

中文翻译：

通过扁平化电荷分离的能量通路从离域激子中提取电子

在有机供体-受体（D-A）界面，电子和空穴结合在一起形成电荷转移（CT）激子。这些 CT 激子中的电子和空穴波函数可以在空间上离域。电子离域化开辟了通过操纵纳米级的势能景观从束缚激子中提取自由电荷的可能性。使用具有级联带结构的原型三层结构，我们表明当中间层的厚度约为 3 nm 时，与双层对应物相比，电荷分离的产率可以加倍。该厚度与通常在这些有机薄膜中发现的 CT 激子的电子离域尺寸一致。三层结构中 CT 状态的紧束缚计算进一步证明了电子离域，与能级级联一起，可以有效地平坦化电荷分离的能量路径。因此，可以在施主和受主之间添加纳米厚的层以显着提高电荷分离率。

更新日期：2021-09-23

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