title: Evidence of Delocalization in Charge-Transfer State Manifold for Donor:Acceptor Organic Photovoltaics.
abstract: 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.
authors.affiliation: Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong , Hong Kong SAR, P. R. China.|Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, P. R. China.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Guan
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, P. R. China.
authors.forename: Ho-Wa
authors.initials: HW
authors.lastname: Li
authors.affiliation: Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong , Hong Kong SAR, P. R. China.|Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, P. R. China.
authors.forename: Jinfeng
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, P. R. China.
authors.forename: Yuanhang
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong , Hong Kong SAR, P. R. China.|Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, P. R. China.
authors.forename: Qingdan
authors.initials: Q
authors.lastname: Yang
authors.affiliation: Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong , Hong Kong SAR, P. R. China.|Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, P. R. China.
authors.forename: Ming-Fai
authors.initials: MF
authors.lastname: Lo
authors.affiliation: Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong , Hong Kong SAR, P. R. China.|Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, P. R. China.
authors.forename: Tsz-Wai
authors.initials: TW
authors.lastname: Ng
authors.affiliation: Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, P. R. China.
authors.forename: Sai-Wing
authors.initials: SW
authors.lastname: Tsang
authors.affiliation: Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong , Hong Kong SAR, P. R. China.|Department of Physics and Materials Science, City University of Hong Kong , Hong Kong SAR, P. R. China.
authors.forename: Chun-Sing
authors.initials: CS
authors.lastname: Lee
keywords: charge-modulated electroabsorption spectroscopy; charge-transfer states; delocalization; organic photovoltaics; polaron states