Highly Twisted Donor-Acceptor Boron Emitter and High Triplet Host Material for Highly Efficient Blue Thermally Activated Delayed Fluorescent Device.

New highly efficient thermally activated delayed fluorescence (TADF) dopant materials (PXB-DI, PXB-mIC) for blue organic light-emitting diode are reported. These materials were designed by combining highly conjugated rigid ring donor moieties and boron acceptor with highly twisted configuration to have high TADF performance and minimized self-quenching properties. In addition, a new high triplet energy and hole transport type host material, PPBI, is also reported. This host represents deeper blue color owing to keeping original spectra of emitters. Fabricated blue TADF device with PXB-mIC in PPBI host exhibited max EQE of 12.5% with CIE of (0.15, 0.08) which is near National Television System Committee blue color. The blue TADF device performances of PPBI host was compared with electron transport type 2,8-bis(diphenylphosphine oxide) dibenzofuran (DBFPO) host. The blue TADF device with PXB-DI in DBFPO host exhibited max EQE of 37.4% in sky blue region. This study demonstrates that our molecular design concept of new emitters and host is beneficial for future high efficiency deep blue TADF devices.