Sterically Shielded Electron Transporting Material with Nearly 100% Internal Quantum Efficiency and Long Lifetime for Thermally Activated Delayed Fluorescent and Phosphorescent OLEDs

• DOI: 10.1021/acsami.7b04391
• Publication Date: 2017-05-15T10:57:24Z
• Authors: Dongdong Zhang; Pengcheng Wei; Deqiang Zhang; Lian Duan
• Keywords: Quantum Efficiency

A high triplet energy (T1) is usually taken as the prerequisite of good exciton confinement electron transporting materials (ETMs); however, there a tradeoff with large mobility and stability. Here, we demonstrated that can also be realized utilizing low-T1 ETM sterically shielding unit. Given short-range interaction Dexter transfer, steric side groups effectively hinder T1 emitters from being quenched by increasing intermolecular distance. Based on this concept, maximum external quantum efficiency (EQEmax) 21.3% was observed in sky-blue thermally activated delayed fluorescence device using ETM, EQE remaining at 21.2% 1000 cd/m2 17.8% 5000 cd/m2. Further, an EQEmax 25.5%, low turn-on voltage 2.3 V, well long T90 over 400 h initial luminance were achieved for green phosphorescent devices. This work highlights viable strategy developing high-performance ETMs, paving their way toward practical applications.