High‐efficiency thermally activated delayed fluorescence materials via a shamrock‐shaped design strategy to enable OLEDs with external quantum efficiency over 38%

To achieve highly-efficient organic light-emitting diodes (OLEDs), great efforts have been devoted into constructing thermally activated delayed fluorescence (TADF) with high horizontal dipole ratios (Θ//). Here, we proposed a design strategy by integrating rigid electron-accepting oxygen-bridged boron core triple electron-donating groups, which exhibited “shamrock-shape”, namely BO-3DMAC and BO-3DPAC. Benefiting from the large-planar skeletons brought shamrock-shaped design, BO-3DPAC exhibit Θ// of 84%/70% 93%/94% in neat/doped films, respectively, finally furnish excellent external quantum efficiencies (EQEs) up to 28.3% 38.7% 20 wt% doped OLEDs sky-blue emission, as well adequate EQEs 21.0% 16.7% nondoped OLEDs. This work unveils promising establish high-Θ// TADF emitters molecular structures using design.