Tuning photophysical and electroluminescent properties of phenanthroimidazole decorated carbazoles with donor and acceptor units: Beneficial role of cyano substitution

Four new multi-functionalized carbazole derivatives featuring phenanthroimidazole, N-phenylcarbazole and cyano-substituents are designed and synthesized. The dyes are characterized by photophysical, electrochemical and thermal properties and the dependency of auxiliary chromophores on the functional properties critically analyzed. The dyes showed tunable emission from violet to blue region depending on the chromophore attached to the carbazole core. The cyano-substituted dyes exhibited enhanced intramolecular charge transfer in optical properties as compared to N-phenylcarbazole substituted dyes. Consequently, cyano-substituted dyes displayed solvatochromism in emission and possess large Stokes shift. All the dyes showed remarkable thermal stability attributable to robust phenanthroimidazole and carbazole chromophores. The fluorescent sensory properties of all the dyes toward acid are also explored and found that the emission of cyano derivatives displayed blue shift due to protonation of phenanthroimidazole unit. Finally, the dyes are employed as dopant emitter in multilayer solution-processed organic light-emitting diode which displayed blue electroluminescence.

Automated summary

Four new multi-functionalized carbazole derivatives with different chromophores exhibit tunable emission spectra, with cyano-substituted dyes demonstrating solvatochromism and enhanced properties in optical and thermal characteristics. The dyes also show good thermal stability and fluorescence modulation towards acid. Additionally, they are successfully applied as dopant emitters in organic light-emitting diodes to achieve blue electroluminescence.