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

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-pi-D-pi-D and D-pi-D-pi-A in our scheme of study. All these designed derivatives consist of a phenothiazine core as central donor fragment (DF), thiophene/furan/pyrrole as pi-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 nm) and emission (524-1103 nm) 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 eV), 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 pi-pi* excitations while the remaining six molecules (PTZ4-PTZ9) displayed ICT in addition to pi-pi* 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.

Automated summary

A series of nine phenothiazine-based derivatives were computationally designed and studied as organic fluorophores. The designed derivatives exhibited broad absorption and emission bands covering visible and infrared regions, with PTZ7-PTZ9 showing the lowest energy levels and energy gaps. The study revealed the potential of PTZ-derivatives as intense and pure color emitters for semiconductor devices.