A theoretical study on the donor ability adjustment of tris(2,4,6-trichlorophenyl)methyl-triarylamine (TTM-TPA) radicals aiming to develop better organic luminescent materials

Abstract

High-performance luminescent radical-based materials are emerging and are in demand for application in organic light-emitting diodes (OLEDs). Herein, quantum chemistry methods are employed to investigate a series of donor–acceptor (D–A) type monoradical molecules based on the tris(2,4,6-trichlorophenyl)methyl (TTM) acceptor and triarylamine (TPA) donor. The major factors affecting the device performance of the monoradical molecules, including thermodynamic stability, excited state characteristics and luminescence properties, are taken into consideration. The introduction of donor fragments can help to tune the luminescent properties of the monoradical molecule, and furthermore, the electron donating abilities of donor fragments, revealed by molecular Mulliken electronegativity, are negatively associated with both the stability and photoluminescence quantum yield (PLQY). The hybrid transition characteristic formed by the combination of charge transfer (CT) and localized excitation (LE) makes a significant contribution to the luminescence intensity of the monoradical molecules. Comparative analyses can lead us to conclude that monoradical molecules 1, 2, 3, 4, 6 and 8 possess more significant stability and photoluminescence efficiency, and are expected to become high-performance luminescent materials. Finally, our investigations show that in order to enhance the thermodynamic stability and PLQY, it should be appropriately considered to weaken the electron donating ability of donor fragments in the TTM-based D–A type of monoradical molecules by rational chemical modifications.