Magnetic Field Effect in Organic Light‐Emitting Diodes Based on Electron Donor–Acceptor Exciplex Chromophores Doped with Fluorescent Emitters. (18th August 2016)

• Record Type: Journal Article
• Authors: Baniya, Sangita; Pang, Zhiyong; Sun, Dali; Zhai, Yaxin; Kwon, Ohyun; Choi, Hyeonho; Choi, Byoungki; Lee, Sangyoon; Vardeny, Z. Valy
• Is Part Of: Advanced functional materials. Volume 26:Number 38(2016)
• Page Start: 6930
• Page End: 6937
• Publication Date: 2016-08-18
• Subjects: delayed fluorescence -- fluorescence emitters -- magneto‐electroluminescence -- magneto‐photoluminescence -- organic light‐emitting diodes -- reverse intersystem crossing; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201601669
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract : A new type of organic light‐emitting diode (OLED) has emerged that shows enhanced operational stability and large internal quantum efficiency approaching 100%, which is based on thermally activated delayed fluorescence (TADF) compounds doped with fluorescent emitters. Magneto‐electroluminescence (MEL) in such TADF‐based OLEDs and magneto‐photoluminescence (MPL) in thin films based on donor–acceptor (D–A) exciplexes doped with fluorescent emitters with various concentrations are investigated. It has been found that both MEL and MPL responses are thermally activated with substantially lower activation energy compared to that in the pristine undoped D–A exciplex host blend. In addition, both MPL and MEL steeply decrease with the emitter's concentration. This indicates the existence of a loss mechanism, whereby the triplet charge‐transfer state in the exciplex host blend may directly decay to the lowest, nonemissive triplet state of the fluorescent emitter molecules. Abstract : Using magneto‐electroluminesence in organic light‐emitting diodes of donor–acceptor exciplex compounds doped with fluorescence emitters, we found that the activation energy of the reversed intersystem crossing process is substantially reduced compared with that of the undoped compound. At lower dopant concentration, the rapid Förster energy transfer enhances the electro‐luminesence, whereas at higher dopant concentration Dexter energy transfer interferes, creating a loss mechanism.