4CzPN is one of three isomers (including 4CzTPN and 4CzIPN) which belong to the carbazolyl benzonitriles (CBC) family. CBC family members are well known, highly efficient thermally activated delayed fluorescence (TADF) materials.
The carbazolyl groups are located next and opposite to the nitrile groups, electrons in 4CzPN orbitals are supposedly more delocalized than its isomers. However, with four bulky carbazolyl groups next to each other, the steric hindrance can reduce the conjugation of the carbazolyl groups to the center benzene ring.