Effect of Multiple Acceptor Structures in Electron Transport Materials on Operational Lifetime of Blue Thermally Activated Delayed Fluorescence Organic Light‐Emitting Diodes

Abstract Recent advances in organic light‐emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF)‐assisted fluorescence (TAF) attest to the great promise of this technology in practical use. However, the simultaneous realization of high efficiency and device durability in blue OLEDs remains a significant challenge. Clarification of the degradation mechanisms correlated to molecular structure and device configuration is the key to extending the device lifetime. In this study, electron transport materials incorporating two triazine units in close proximity are adopted to use in hole‐blocking and electron‐transporting layers, resulting in superior device performances. In addition, a modified photodegradation experiment reveals that the degradation origins closely relate to charge carriers. The optimization of the device according to the obtained findings leads to 4.5 times extension in the lifetime of the TAF‐OLED using a multiple resonance emitter. These results also provide guidelines for designing robust electron transport materials for blue OLEDs.