Blueprints for Brightness: A Trilogy of Locking, Substitution, and Extension Strategies in Carbonyl–Nitrogen‐Based MR‐TADF Emitters

Multiresonant thermally activated delayed fluorescence (MR‐TADF) materials have emerged as next‐generation OLED emitters owing to their narrowband emission, high color purity, and potential for 100% exciton utilization. Among the various MR‐TADF scaffolds, carbonyl/nitrogen‐based, quinolino[3,2,1‐de]acridine‐5,9‐dione (QAO) cores have attracted significant attention due to their modularity and electronic tunability. This review article presents a systematic analysis of recent advancements in QAO‐based emitters, categorized into three molecular design strategies: core locking, core substitution, and core extension. Core locking enhances rigidity, minimizes vibrational loss, and narrows emission profiles critically mandated by blue‐emitting MR‐TADF systems. Substitution at key positions enables fine control over emission wavelength, Δ E ST , and photoluminescence quantum yield (Φ PL ). Core extension via π ‐conjugation elongation or fused aromatic units leads to improved device efficiencies and diverse emission colors, including green and deep‐blue electroluminescence. Collectively, these strategies have produced emitters with Φ PL exceeding 90%, EQEs above 30%, and full‐width half maximums as low as 20 nm. We conclude by highlighting current limitations, including RISC bottlenecks, doping concentration effects, and synthetic challenges, while proposing design pathways toward next‐generation multifunctional, solution‐processable, and chiral MR‐TADF materials. This review article provides a roadmap for advancing carbonyl‐nitrogen based MR‐TADF emitters toward high‐performance OLED technologies.