High Performance All Fluorescence White Organic Light Emitting Devices with a Highly Simplified Structure Based on Thermally Activated Delayed Fluorescence Dopants and Host

Thermally activated delayed fluorescence (TADF) emitters of different colors commonly need different hosts, which cause the complexed device structure and low efficiency of all fluorescence white organic light-emitting devices (F-WOLEDs). To solve this, novel concept of employing TADF exciplex as universal host of TADF emitters with different colors was proposed. All blue, green, and orange devices based on the TADF exciplex host show much lower turn-on voltages, and comparable and even higher efficiencies than corresponding devices based on conventional hosts. The two color F-WOLED with extremely simplified device structure was finally fabricated, achieving a white emission with the maximum current efficiency (CE), power efficiency (PE), and external quantum efficiency (EQE) respectively of 50.1 cd A^-1, 63.0 lm W^-1, and 19.0% in the forward-viewing direction without any light out-coupling technology, which is the best performance among reported F-WOLEDs, demonstrating the superiority of the novel concept.