Highly Luminescent Aluminum Complex with β-Diketone Ligands Exhibiting Near-Unity Photoluminescence Quantum Yield, Thermally Activated Delayed Fluorescence, and Rapid Radiative Decay Rate Properties in Solution-Processed Organic Light-Emitting Devices

A highly luminescent mononuclear Al complex with beta-diketone ligands exhibiting superior thermally activated de-layed fluorescence (TADF) properties was developed in this work. The complex showed yellow emission with promising photofunctions, including a near-unity photoluminescence quantum yield (PLQY), a rapid radiative decay rate, and a short delayed fluorescence lifetime in the solid state. When applied in a solution-processed organic light-emitting device, an external quantum efficiency (EQE) exceeding 18% and a low turn-on voltage of 2.9 V at 1 cd/m2 were obtained, sur-passing those of the corresponding beta-diketone ligand. Metal complexation with Al generated unique electronic structures that significantly strengthened the photofunctions of the origi-nal beta-diketone ligand in the solid state.