Dibenzothiophene-Based Phosphine Oxide Host and Electron-Transporting Materials for Efficient Blue Thermally Activated Delayed Fluorescence Diodes through Compatibility Optimization FanChaochao DuanChunbo WeiYing DingDongxue XuHui HuangWei 2015 Thermally activated delayed fluorescence (TADF) organic light-emitting diodes arise from the development of high-performance host materials and carrier transporting materials fitting for TADF dyes with optimized respective properties and interplays, making simultaneous performance improvement and device structure simplification feasible. In this work, a highly efficient blue TADF diode with simplified four-layer structure was successfully achieved by utilizing bis­[4-(9,9-dimethyl-9,10-dihydroacridine)­phenyl]­sulfone (<b>DMAC</b>-<b>DPS</b>) as blue emitter, 4,6-bis­(diphenylphosphoryl)­dibenzothiophene (<b>DBTDPO</b>) as host, and 4,6-bis­(diphenylphosphoryl)­dibenzothiophene sulfone (<b>46DBSODPO</b>) as electron-transporting layer. The compatibilities between <b>DBTDPO</b> and <b>DMAC</b>-<b>DPS</b> and <b>DBTDPO</b> and <b>46DBSODPO</b> were optimized with respect to configuration, polarity, energy level, and interfacial interaction, resulting in the unchanged roughness of ∼0.25 nm before and after doping, high photoluminescence quantum yield over 85%, and reduced interfacial exciplex emissions. With the similar triplet excited energy (<i>T</i><sub>1</sub>) of ∼3.0 eV but inferior electrical properties compared to its analogues <b>28DBSODPO</b> and <b>37DBSODPO</b>, besides the homogeneity with <b>DBTDPO</b>, <b>46DBSODPO</b> suppressed the formation of interfacial exciplex and dipole for efficient exciton confinement and electron injection and transportation, in virtue of the steric effects of its <i>ortho</i>-substituted phosphine oxide groups. Consequently, <b>DBTDPO</b> and <b>46DBSODPO</b> endowed their <b>DMAC</b>-<b>DPS</b> based four-layer devices with the state-of-the-art performance, for example, the maximum external quantum efficiency over 16%, which was more than two-fold of those of conventional electron-transporting material 1,3,5-tri­[(3-pyridyl)-phen-3-yl]­benzene (<b>TmPyPB</b>). This design strategy about material compatibility could pave a way for developing high-performance blue TADF diodes with simplified configurations.