Dimesitylarylborane-based luminescent emitters exhibiting highly-efficient thermally activated delayed fluorescence for organic light-emitting diodes

作者：Kitamoto Yuichi; Namikawa Taketo; Suzuki Takatsugu; Miyata Yasuo; Kita Hiroshi; Sato Tetsuo; Oi Shuichi

来源：Organic Electronics, 2016, 34: 216-225.

DOI：10.1016/j.orgel.2016.04.030

• Thermally activated delayed fluorescence
• Organic light-emitting diodes
• Donor-acceptor triarylborane

Triarylboranes are widely used as luminescent molecules. However, there are few reports focused on thermally activated delayed fluorescence (TADF) characteristics. In this study, new donor-acceptor triarylboranes exhibiting TADF characteristics are designed, synthesized, and applied to organic light-emitting diodes (OLEDs) as an emitter. Electro-accepting dimesitylphenylborane connected with carbazole (7), 9,9-dimethylacridane (8), and phenoxazine (9) as electron-donating units are synthesized in only two steps with good yield. Compounds 8 and 9 exhibit light blue and green TADF with good PL quantum yields of 89 and 87% in toluene, respectively. On the other hand, compound 7 shows normal deep blue fluorescence without TADF characteristics. Density functional theory and time-dependent density functional theory studies reveal that high electron-donating ability of donor unit and large dihedral angles between cross-linking phenylene and donor units are attributed to spatially separate the HOMO and LUMO, which results in lowering the energy gap between lowest singlet (S-1) and triplet (T-1) excited states and accelerating reverse intersystem crossing of excitons from T-1 to S-1 states. OLEDs using compounds 8 and 9 as emitters exhibit light blue and green emission with very good external quantum efficiencies of 16.0 and 17.3%, respectively.

• 出版日期2016-7