title: Charge-transfer complexes and their role in exciplex emission and near-infrared photovoltaics.
abstract: Charge transfer and interactions at organic heterojunctions (OHJs) are known to have critical influences on various properties of organic electronic devices. In this Research News article, a short review is given from the electronic viewpoint on how the local molecular interactions and interfacial energetics at P/N OHJs contribute to the recombination/dissociation of electron-hole pairs. Very often, the P-type materials donate electrons to the N-type materials, giving rise to charge-transfer complexes (CTCs) with a P(δ+) -N(δ-) configuration. A recently observed opposite charge-transfer direction in OHJs is also discussed (i.e., N-type material donates electrons to P-type material to form P(δ-) -N(δ+) ). Recent studies on the electronic structures of CTC-forming material pairs are also summarized. The formation of P(δ-) -N(δ+) -type CTCs and their correlations with exciplex emission are examined. Furthermore, the potential applications of CTCs in NIR photovoltaic devices are reviewed.
authors.affiliation: Center of Super-Diamond and Advanced Films (COSDAF), Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR, P. R. China; City University of Hong Kong Shenzhen Research Institute, Shenzhen, People's Republic of China.
authors.forename: Tsz-Wai
authors.initials: TW
authors.lastname: Ng
authors.forename: Ming-Fai
authors.initials: MF
authors.lastname: Lo
authors.forename: Man-Keung
authors.initials: MK
authors.lastname: Fung
authors.forename: Wen-Jun
authors.initials: WJ
authors.lastname: Zhang
authors.forename: Chun-Sing
authors.initials: CS
authors.lastname: Lee
keywords: charge-transfer complexes; electronic coupling; excitons; organic light-emitting diodes (OLEDs); organic photovoltaics (OPV)