Click-To-Twist Strategy To Build Blue-to-Green Emitters: Bulky Triazoles for Electronically Tunable and Thermally Activated Delayed Fluorescence.

Discovery of a new chemical moiety is the foundation to build new functional materials. For charge-transfer-type thermally activated delayed fluorescence (TADF) emitters, donor, acceptor, and π-spacer are the three key structural components. We invented a "click-to-twist" strategy to prepare a triazole-based acceptor unit that allows for a systematic modulation of the electronic and steric properties to control the excited-state photophysics. Taking the modular approach, six different emitters were prepared by varying the donor strength and π-spacer sterics for mix-and-match. These materials display deep blue to sky blue emissions in solutions, as well as apparent TADF characteristics in doped films. Organic light emitting diodes fabricated with these new TADF materials exhibit high external quantum efficiencies of up to 20.7% and maximum luminance of 6823 cd m-2. Building upon an intuitive and operationally straightforward method to build sterically congested molecules, this work showcases a new strategy to diversify TADF emitters by a mechanism-based design and modular synthesis.