The effect of substituted 1,2,4-triazole moiety on the emission, phosphorescent properties of the blue emitting heteroleptic iridium(III) complexes and the OLED performance: a theoretical study.

A series of neutral heteroleptic mononuclear iridium(III) complexes was investigated using the density functional theory/time-dependent density functional theory approach to determine the effect of the substituted 1,2,4-triazole moiety on the electronic structures, emission, and phosphorescent properties and the organic light emitting diode (OLED) performance. The results reveal that substitution of the free position in the triazole ring by -PhOCH3 (2) provides a higher emission energy and a lower oscillator strength, leading to longer radiative lifetime values mainly due to the ligand-to-ligand charge transfer transition character. The evaluation, based on one-center spin-orbit coupling, results in higher kr values for the substituent -F5Ph (5) and a lower ΔE(S-T) value. Furthermore, we also investigated the performance of the OLED device, including the charge injection/transport/balance ability, increases in the Förster energy transfer rate and triplet exciton confinement for host and guest materials of blue emitting Ir(III) complexes. Finally, we hope that our investigations will help in the design of highly efficient phosphorescent materials.