Synthesis, characterization and structure-property study of new push-pull carbazole materials

In the present work, we deal with some new organic materials having an extended conjugated electron system and providing tunable intramolecular charge transfer (ICT) properties. Firstly, the material structure, taken as a reference, is based on the N-ethylcarbazole motive as a central core having two bromo-distyrylbenzene units, denoted as M1, and has been synthesized and characterized principally using thermograviometric (ATG), absorption (OA), and emission spectroscopy (PL). Then, some derived compounds as symmetrical push-pull type materials with variations in their acceptor/anchor groups, containing four different kind of electron acceptor (A) groups and the ethylcarbazole as electron donor (D) part, denoted as CbzA1. 4 were designed and elucidated. The impact of different electron-accepting strengths on the photophysical properties of carbazole derivatives is discussed. The correlation between structure properties of these materials has been well established. The withdrawing acceptor effect on their geometrical structure and optoelectronic properties was elucidated. In this framework, quantum calculations, based on density functional theory (DFT) and time-dependent DFT (TD-DFT) methods, in both gas and solution phases, agree well with the experimental results. The lowest lying absorption and fluorescence spectra are the signatures of intramolecular charge transfer (ICT) character. Additionally, N-donor substitution was used to modulate the photophysical properties of these push-pull compounds and thus the organic based photovoltaic device's performance.