Mixed-Host Systems with a Simple Device Structure for Efficient Solution-Processed Organic Light-Emitting Diodes of a Red-Orange TADF Emitter.

Charge balance, concentration quenching, and exciton confinement are the most important factors for realizing the use of thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes. Red-orange organic light-emitting diodes of a TADF emitter 2-[4 (diphenylamino)phenyl]-10,10-dioxide-9H-thioxanthen-9-one (TXO-TPA) have been reported by doping in a mixed p-type host system of poly(N-vinylcarbazole) (PVK) and 1,3-bis(N-carbazolyl)benzene (mCP) via solution-processed. We have demonstrated the peak external quantum efficiency of 9.75%, maximum current efficiency of 19.36 cd/A, and power efficiency of 12.17 lm/W along with a CIE coordinate of (0.45, 0.51). The devices were compared with different doping concentrations of TXO-TPA, and a comparative investigation on the effect of the thickness electron transport layer was studied. The results clearly indicated that this solution-processed TXO-TPA device structure is a promising strategy to develop highly efficient but simple OLED structures.