Charge transfer (CT) complexes, formed by electron transfer from a donor to an acceptor, play a crucial role in organic semiconductors. Excited-state CT complexes, termed exciplexes, harness both singlets and triplets excitons for light emission, and are thus useful for organic light-emitting diodes (OLEDs). However, present exciplex emitters often suffer from low photoluminescence quantum efficiencies (PLQEs), due to limited control over the relative orientation, electronic coupling and non-radiative recombination channels of the donor and acceptor subunits.
Recently, Prof. Liang-Sheng Liao and Prof. Zuo-Quan Jiang from Soochow University, collaborated with Prof. Richard H. Friend from Cavendish Laboratory of University of Cambridge, proposed a strategy to use a rigid linker to control the spacing and relative orientation of the donor and acceptor subunits, as demonstrated with a series of intramolecular exciplex emitters based on 10-phenyl-9,10-dihydroacridine and 2,4,6-triphenyl-1,3,5-triazine, and eventually realized high efficiency luminescence. The highlights of this research include:
Sky-blue OLEDs employing one of these emitters achieve an external quantum efficiency (EQE) of 27.4% at 67 cd m−2 with only minor efficiency roll-off (EQE = 24.4%) at a higher luminous intensity of 1,000 cd m−2.
The design rules of space and relative orientation control are transferrable to other donor/acceptor combinations, which will allow further tuning of emission colour and other key optoelectronic properties.
This research has been published in Nature Materials (https://doi.org/10.1038/s41563-020-0710-z) titled as “Highly efficient luminescence from space-confined charge-transfer emitters”. This strategy will offer an avenue for further studying and utilizing through-space electronic interactions in optoelectronic materials.
Link to paper: https://www.nature.com/articles/s41563-020-0710-z
Link to Prof. Liao’s group: http://funsom.suda.edu.cn/funsomen/c4/00/c3002a50176/page.htm
Editor: Danting Xiang