Extended Theoretical Investigations Based on The Best Light-Emitting Electrochemical Cell (LEEC) Champions Reported in Early 2022

The emission spectra and phosphorescence quantum yield of top-performing iridium (III) complexes, each containing distinct cyclometallated ligands, were analyzed using density functional theory (DFT) and time-dependent DFT (TD-DFT) approaches. The computed photophysical properties of these iridium complexes aligned well with the experimental data. All complexes show emissions characterized as a mixture of triplet ligand-to-ligand charge transfer (3LLCT) and metal-to-ligand charge transfer (3MLCT) states. The vertical emission energies calculated at the B3LYP level for the 1–4 complexes are located at 2.7, 2.4, 2.1, and 2.9 eV, respectively. Based on these results, theoretical calculations can provide accurate predictions of the electronic and photophysical properties of iridium complexes and then can be used to guide the synthesis of new phosphorescent materials.