A low‐cost facile synthesis of solution processable N‐phenylcarbazole/triazine hybrid host for orange TADF OLEDs

An N‐phenylcarbazole/triazine hybrid of 2,4,6‐tris(9‐phenyl‐9H‐carbazol‐3‐yl)‐1,3,5‐triazine ( TPhCz‐Trz ) is successfully synthesized using cheap raw materials via facile synthesis method with a high yield of 60.9%. Good thermal ( T d , 284 °C) and morphological stability are realized due to its rigid structure and three‐dimensional steric hindrance. The high triplet energy level of 2.88 eV for the host is very important to inhibit the energy reverse from guest to host. Surprisingly, orange thermally‐activated delayed fluorescent (TADF) organic light‐emitting diodes (OLEDs) are achieved by using excellent green emitter 9,10‐bis(4‐(3,6‐ditertbutyl‐9H‐carbazol‐9‐yl)‐2,6‐dimethyl‐phenyl)‐9,10‐diboraanth‐racene (tBuCzDBA) with the maximum external quantum efficiency of 14.0%. The large bathochromic‐shift is probably induced by the polarity of the host compared to the emission peak of 542 nm of tBuCzDBA‐based green TADF device. This indicates high performance of devices with different colors would be achieved through optimizing molecular structure of the host and device framework using tBuCzDBA as emitter.