Design Strategy of Decorating Phenylcarbazole with a Donor and Acceptor for Blue‐Shifted Emission in Thermally Activated Delayed Fluorescent Emitters

A series of blue thermally activated delayed fluorescent (TADF) emitters of 1′′‐(4,6‐diphenyl‐1,3,5‐triazin‐2‐yl)‐9,9′′‐diphenyl‐9H,9′′H‐3,3′:9′,4′′‐tercarbazole (TrzCz1) and 3′,6′‐di‐tert‐butyl‐1‐(4,6‐diphenyl‐1,3,5‐triazin‐2‐yl)‐9‐phenyl‐9H‐4,9′‐bicarbazole (TrzCz2) were synthesized through a molecular design approach to decorate phenylcarbazole with a donor and an acceptor. The 1‐ and 4‐positions of the phenylcarbazole core were modified with a diphenyltriazine acceptor and a bicarbazole or tert‐butylcarbazole donor, respectively, through a synthetic strategy to introduce Br at the 1‐position and F at the 4‐position. The TrzCz1 and TrzCz2 emitters showed maximum photoluminescence emission bands at λ=443 and 433 nm, which were blueshifted relative to those of the corresponding TADF emitters with the same donor and acceptor, respectively. In the device application, the TrzCz1 emitter showed a maximum external quantum efficiency of 22.4 %, with a color coordinate of (0.16, 0.21), and the TrzCz2 emitter showed a maximum external quantum efficiency of 9.9 %, with a color coordinate of (0.14, 0.09). This work proved that the design strategy of decorating phenylcarbazole with a donor and an acceptor is effective at blueshifting the emission of TADF emitters. Playing the blues: A phenylcarbazole core was modified with a diphenyltriazine acceptor and a bicarbazole or tert‐butylcarbazole donor to prepare thermally activated delayed fluorescent (TADF) emitters. These new emitters showed maximum photoluminescence emission bands that were blueshifted, relative to those of the corresponding TADF emitters with the same donor and acceptor, and thus, were suitable for application in blue organic light‐emitting diodes.