Realizing Stable Narrowband Emission Blue Fluorescent Organic Light-Emitting Diodes with Dual-Channel Triplet Exciton Harvesting Host

Exciton annihilation is one of the main factors affecting the operational lifetimes of organic light-emitting diodes (OLEDs). Constructing an appropriate host–emitter system is helpful in reducing the exciton annihilation process and has a positive influence on the stability of the device. Herein, a "hot exciton" fluorescent material PAC with dual-channel triplet exciton harvesting ability including reverse intersystem crossing from high-lying triplet states and triplet–triplet annihilation has been explored as the host of narrowband multiresonance thermally activated delayed fluorescence blue emitter JBD-1 to achieve a long device lifetime. The exciton quenching of the host–emitter system is alleviated by the energy transfer of the long-lived triplet excitons from the first triplet state (T1) of JBD-1 to the T1 of PAC, leading to lower defect formation rate and more stable device. A device lifetime of LT50 = 458 h at the initial luminance of 1000 cd m–2, an EQE of 7.6%, and Commission International de l'Eclairage coordinates of (0.13, 0.11) were achieved in bottom emission OLEDs, while the operational lifetimes of the devices based on conventional hosts MCP and MADN are only 0.37 and 1.09 h, respectively. This work suggests a way for constructing stable and narrowband emission blue fluorescent OLEDs in the perspective of host.