Design and Synthesis of N-Heterocyclic Donor Based TADF Emitters for Application in OLEDs

As one of the most promising electroluminescent technologies, thermally activated delayed fluorescence (TADF) OLEDs have attracted more and more attention due to their enormous and unique potential for application in industrial products. The presented work is focused on the development of new TADF emitters for OLEDs. Particularly, emitters for blue TADF emission are thoroughly investigated via the evaluation of newly designed and modified N-heterocyclic donors. In the first part, TADF emitters based on N-heterocyclic donors and boron-containing acceptors were designed and synthesized. Photophysical studies revealed that blue emission was accessed through the variation of the N-heterocyclic donors. Secondly, a series of TADF emitters derived from the indolocarbazole donors and di-phenyltriazine acceptors were evaluated. OLED with the EQE of over 22.1% and sky-blue emission at 483 nm was obtained. Lastly, deep blue TADF emission was realized by introducing electron-withdrawing groups to the [2.2]paracyclophane-derived donor unit. For further decreasing the DeltaE?ST to harvest more efficient TADF molecules, through-space donor dimers and the corresponding emitters were also synthesized, yielding blue TADF emission.