Boron- and Silane-Based Electron Transport–Type Host Materials for Long-Lifetime Blue Phosphorescent Organic Light-Emitting Diodes

Developing new host materials is crucial to enhance the performance of blue organic light-emitting diodes (OLEDs), but achieving long operational lifetimes for OLEDs has been challenging. In this study, boron- and silane-based electron transport–type (n-type) host materials, 5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yltriphenylsilane (BO-pSi) and 2,12-bis(triphenylsilyl)-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene (BO-2mSi), derived from boron- and oxygen-based 5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene (DOBNA) are developed. The DOBNA derivatives are modified with a triphenylsilyl blocking group to alleviate intermolecular interactions arising from the planar structure of DOBNA. The DOBNA derivatives maintain high triplet energy even in the solid state and show thermally activated delayed fluorescence features with electron transport properties. BO-pSi is used as an n-type host and exhibits a long operational lifetime of ≈5000 h up to 50% of the initial luminance of blue phosphorescent OLEDs. Furthermore, BO-2mSi demonstrates a high external quantum efficiency of 7.1%, a small full width at half maximum of 33 nm, and a pure-violet color coordinate of (0.16, 0.02) while maintaining color purity even at high doping concentrations up to 50 wt%.