A six-carbazole-decorated cyclophosphazene as a host with high triplet energy to realize efficient delayed-fluorescence OLEDs

A high triplet energy (ET) host material, hexakis(9H-carbazol-9-yl) cyclotriphosphazene (PzCz), is used in high-efficiency organic light-emitting diodes (OLEDs). PzCz (E-T = 3.00 eV) functions as an effective host for thermally activated delayed fluorescence (TADF) molecules. Highest external electroluminescence quantum efficiencies over 15% and 18% are achieved for blue-green and green TADF-OLEDs, respectively.