Ubiquitous Aluminum(III)‐TADF Complex as Sensitizer for Highly Efficient Solution‐Processed Hyperfluorescent OLEDs with Narrow Emission

Although Earth‐abundant, ubiquitous, metal‐based thermally activated delayed fluorescence (TADF) complexes are among the most promising candidate materials for next‐generation organic light‐emitting devices (OLEDs), few complexes are explored. Herein, a highly emissive aluminum(III)‐TADF complex— Al(MCzDBM) 3 —with three β‐diketone ligands is presented as a sensitizer for multiresonance (MR)‐TADF emitters. This complex exhibited green emission with suitable photophysical functions as a sensitizer, such as a high photoluminescent quantum yield (PLQY) of up to 97% with reduced aggregation‐caused quenching, a high radiative rate constant ( k r ) of 5.6 × 10 7 s −1 , and a short delayed lifetime (τ d ) of 4.0 µs in the solid state. A solution‐processed Al(MCzDBM) 3 ‐based OLED exhibited an external quantum efficiency (EQE) of 23.6%. This complex sensitized a yellow MR‐TADF emitter, yielding a near‐unity PLQY, and is used to fabricate a solution‐processed hyperfluorescent OLED with an EQE of 21.6% and full width at half maximum of 45 nm.