Tetracoordinate Boron-Based Multifunctional Chiral Thermally Activated Delayed Fluorescence Emitters.

Purely organic emitters have shown great potential but still suffer from low efficiency in near-infrared organic light-emitting diodes (NIR-OLEDs) due to the intensive non-radiative recombination. In this contribution, two pairs of thermally activated delayed fluorescence (TADF) enantiomers (R/S-DOBP and R/S-HDOBP) with tetracoordinate boron geometries were designed and synthesized. The TADF emitters simultaneously showed aggregation-induced emission, circularly polarized luminescence, high-contrast mechanochromism, and piezochromism behaviors. More importantly, R/S-DOBP and R/S-HDOBP revealed high photoluminescence quantum yields and efficient reverse intersystem crossing in neat films. The nondoped solution-processed OLEDs based on these unique emitters revealed the NIR emission (peaking at 716 nm) with a maximum external quantum efficiency of 1.9 % and high exciton utilization efficiency of 86 %, which represent one of the best solution-processed nondoped NIR-OLEDs.