4CzPN-Me, namely 3,4,5,6-tetrakis(3,6-dimethylcarbazol-9-yl)- 1,2-dicyanobenzene, is a fully methylated derivative of 4CzPN at 3,6-positions with four carbazole moieties either next or opposite to the cyano groups. The methyl groups on each of the carbazolyl moieties not only increase the solubility of 4CzPN-Me while comparing with 4CzPN by the introduction of solubilizing alkyl groups with enhanced steric effect, but also enrich the electron density of the carbazole units around the benzene ring.
Also comparing with 4CzPN, the photoluminescence of 4CzPN-Me is red-shifted due to the higher degree of electron density and conjugation.