Evidence of Delocalization in Charge-Transfer State Manifold for Donor:Acceptor Organic Photovoltaics

How charge-transfer states (CTSs) assist charge separation of a Coulombically bound exciton in organic photovoltaics has been a hot topic. It is believed that the delocalization feature of a CTS plays a crucial role in the charge separation process. However, the delocalization of the “hot” and the “...

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Bibliographic Details
Published in:ACS applied materials & interfaces 2016-08, Vol.8 (33), p.21798-21805
Main Authors: Guan, Zhiqiang, Li, Ho-Wa, Zhang, Jinfeng, Cheng, Yuanhang, Yang, Qingdan, Lo, Ming-Fai, Ng, Tsz-Wai, Tsang, Sai-Wing, Lee, Chun-Sing
Format: Article
Language:English
Subjects:
solar energy
spectroscopy
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Summary:How charge-transfer states (CTSs) assist charge separation of a Coulombically bound exciton in organic photovoltaics has been a hot topic. It is believed that the delocalization feature of a CTS plays a crucial role in the charge separation process. However, the delocalization of the “hot” and the “relaxed” CTSs is still under debate. Here, with a novel frequency dependent charge-modulated electroabsorption spectroscopy (CMEAS) technique, we elucidate clearly that both “hot” and “relaxed” CTSs are loosely bound and delocalized states. This is confirmed by comparing the CMEAS results of CTSs with those of localized polaron states. Our results reveal the role of CTS delocalization on charge separation and indicate that no substantial delocalization gradient exists in CTSs.
ISSN:1944-8244
1944-8252
1944-8252
DOI:10.1021/acsami.6b06010