White Light Emission Achieved by Dual-TADF in a Single Emissive Layer of Multicomponent Emitters

Abstract

White light emission (WLE) from multicomponent organic systems has attracted significant attention in recent years due to easy access of bright blue and yellow/orange, or red emitters. However, realizing WLE from a single emissive layer of multicomponent organic thermally activated delayed fluorescence (TADF) systems is an exasperating task due to uncontrolled Förster energy transfer and Dexter-type triplet–triplet energy transfer (TTET). To address this issue, we demonstrated WLE using blend films (WL1, WL2, and WL3) of blue (CPPN, CQ, and DMOC-DPS) and orange (PTzQ) TADF emitters. WL1 comprises CPPN and PTzQ, while DMOC-DPS and PTzQ were used to construct WL2. Spectroscopic analysis revealed that WL1 and WL2 exhibited dual emission features (quantum yields = 48–54%; Commission Internationale de l’éclairage coordinates: 0.34, 0.31; 0.31, and 0.34) via simultaneous blue- and orange-TADF covering the visible region. The WLE feature is observed due to (i) similar absorption and different Stokes shifted emission color of both the emitters and (ii) the absence of TTET caused by large triplet–triplet gaps (>0.4 eV) between the emitters. In contrast, WLE via fluorescence and TADF was observed in WL3 due to TTET. This finding is expected to provide new insights for designing high-energy-efficient WLE for white organic light-emitting diodes.