Tuning a Weak Emissive Blue Host to Highly Efficient Green Dopant by a CN in Tetracarbazolepyridines for Solution‐Processed Thermally Activated Delayed Fluorescence Devices

Cyanopyridine is used as a new electron-withdrawing unit for thermally activated delayed fluorescence (TADF). Solution-processed simple structure devices using 2,3,5,6-tetracarbazole-4-cyano-pyridine as a green TADF dopant show maximum external quantum efficiencies as high as 10.4% and 11.4% for devices with 2,3,5,6-tetracarbazole-pyridine and 1,3-bis(N-carbazolyl)benzene as host materials, respectively.