Highly efficient exciplex organic light-emitting diodes by exciplex dispersion in the thermally activated delayed fluorescence host

In this work, we describe a new approach of improving the external quantum efficiency (EQE) of exciplex organic light-emitting diodes (OLEDs). A new approach of dispersing the exciplex in the thermally activated delayed fluorescence (TADF) host was developed to increase the EQE of the exciplex OLEDs. The new emitting layer structure was made up of a mixture of TADF material and an n-type material which can generate exciplex with the TADF material. The content of the n-type material was maintained below 10 wt % to have a morphology with the exciplex dispersed in the TADF matrix material. The emitting layer structure with the exciplex dispersed in the TADF host suppressed exciton quenching and improved the photoluminescence quantum yield of the exciplex. As a result, the exciplex OLEDs with the n-type material content of 1 wt% showed high EQE of 15.3% compared with EQE of 10.8% of the conventional exciplex OLEDs with the n-type material content of 50%.