DFT and TD-DFT studies of phenothiazine based derivatives as fluorescent materials for semiconductor applications

Abstract

Abstract A series of nine phenothiazine-based derivatives (PTZ1-PTZ9) have been computationally designed and investigated as organic fluorophores by employing two different topologies i.e., D-π-D-π-D and D-π-D-π-A in our scheme of study. All these designed derivatives consist of a phenothiazine core as central donor fragment (DF), thiophene/furan/pyrrole as π-spacers (P1/P2/P3), triphenylamine as terminal electron donor unit (DF1), and terminal acceptor unit (A1/A2). The effect of these substituents was studied on their optoelectronic and stability characteristics. TD-DFT calculations explores that bathochromically-shifted absorption (423–994\xa0nm) and emission (524–1103\xa0nm) bands of the designed derivatives cover the visible region and are also extended to the infrared regions of the spectrum. Among all designed fluorescent emitters, PTZ7-PTZ9 derivatives exhibit the lowest energy levels, energy gaps (1.44–1.57\xa0eV), exclusive broad absorption, and emission peaks owing to their strong electron-withdrawing fragments. The computational analysis of frontier molecular orbitals, population analysis, and natural transition orbital analysis has revealed that PTZ1-PTZ3 derivatives exhibited π-π* excitations while the remaining six molecules (PTZ4-PTZ9) displayed ICT in addition to π-π* electronic transitions. The dipole moments of all investigated molecules (3.30–18.78 D) are higher than the reference molecule (2.20 D), indicating their greater solubility in dichloromethane solvent. The nine newly designed fluorescent materials are also studied for their charge transport/injection properties like radiative lifetime and light harvesting efficiency. This theoretical study has disclosed PTZ-derivatives as potential fluorescent emitters with intense and pure color emission for semiconductor devices.