Enhancing the efficiency of red TADF OLED by optimizing the guest-host matrix and charge balance engineering

Charge (electrons and holes) balance engineering is employed to demonstrate an enhancement in the performance of organic light emitting diodes (OLEDs) fabricated with a near infra red thermally activated delayed fluorescence (TADF) molecule 7,10-Bis(4-(diphenylamino)phenyl)-2,3-dicyanopyrazino phenanthrene (TPA-DCPP). The emissive layer of the OLED comprises of a guest-host matrix. A detailed analysis of the choice of host that is to be employed in the guest-host matrix of the emissive layer of the OLED is presented. The doping concentration of the guest in the emissive layer is optimized by photoluminescence (PL) studies. A comparative analysis of 1,4,5,8,9,11-Hexaazatriphenylenehexacarbonitrile (HATCN) and Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) PEDOT: PSS as hole injection layers and their effect on device efficiency and charge balance in the emissive layer of the device stack is presented. From the study, a red TADF OLED with a maximum external quantum efficiency of 13.2% at a luminance of 1 cd/m2 is demonstrated.