Could organoaluminium complexes act as prominent TADF emitters for designing efficient diode devices? A DFT/TDA simulation study

Theoretical calculations suggest possible designs of Thermally Activated Delayed Fluorescence (TADF) emitters using three-coordinate aluminium (Al-X₃) complexes for the design of organometal light emitting diodes. We investigate the optical properties of gas-phase and toluene-solvated Ac-Al, Ac-Al-F, Ac-Al-CN and Ac-Al-NO₂ complexes using DFT/TDA methods. All calculations were carried out using the long-range corrected ωB97XD functional with optimal ω values. Except for Ac-Al-CN contender, the aluminum atom has magnified the spin–orbit couplings between the excited singlet (S₁) and triplet (T₁) states. The decrease in the reorganization energies of Ac-Al-CN and Ac-Al-NO₂ complexes has maximized their reverse intersystem crossing rate constants. The presence of the strong electron withdrawing nitro group has further stabilized its LUMO together with improving both its oscillator strength and the emission decay rate constant. This contender is predicted to be the most prominent TADF emitter and highly promising for designing diode devises amongst the understudy complexes.