Applications of exciplex emission in thermally activated delayed fluorescent OLEDs

Exciplex emissions are emissions from excited state complexes formed between specific combinations of donor and acceptor molecules. Their emission spectra are typically red shifted and board comparing to those of their constituting molecules. While exciplex emissions had been considered to be harmful for device performance a couple of decades ago, their applications in high performance OLEDs have been demonstrated in the past few years. In particular, their applications in thermally activated delayed fluorescent (TADF) OLEDs have attracted much recent attention. In this talk, several aspects on exciplex emissions and their applications in TADF OLEDs will be addressed. Firstly, the criteria for selecting donor (D) and acceptor (A) molecules for giving exciplex emissions will be discussed [1]. The conditions required for an exciplex emitter to give TADF is then explained [1]. Examples on applications of TADF exciplex emitters in OLEDs of different structures will be provided. In particular, device design involving doping of conventional fluorescent dopants [2], phosphorescent dopants [3], as well as TADF dopants [4] in hosts of TADF exciplex emitters will be discussed.