Recent Advances in Blue Multiple‐Resonance Thermally Activated Delayed Fluorescence Materials and their Applications in Organic Light‐Emitting Diodes

Abstract Multi‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters have attracted considerable academic and industrial attention because of their narrowband emission, high photoluminescence quantum yields (PLQYs), and exceptional chemical and thermal stability. These characteristics make them highly promising for applications in ultra‐high‐definition (UHD) displays, as they enable organic light‐emitting diodes (OLEDs) with high color purity, superior efficiency, and outstanding operational stability. Nevertheless, the development of highly efficient and stable deep‐blue OLEDs remains a critical and unresolved challenge. Recent advances in blue MR‐TADF emitters, based on boron/nitrogen‐, nitrogen/carbonyl‐, and indolocarbazole‐type MR systems, have yielded exceptional performance, with full‐width at half‐maximum (FWHM) values below 30 nm and external quantum efficiencies (EQEs) exceeding 30%. Despite these achievements, persistent issues such as aggregation‐caused quenching (ACQ), efficiency roll‐off, and device stability continue to impede further progress in blue‐emitting OLEDs. This review comprehensively summarizes recent developments in blue MR‐TADF materials and devices, focusing on their molecular design strategies aimed at tuning emission color, mitigating ACQ, as well as improving device efficiency and operational lifetime. The discussed insights are expected to accelerate the development of high‐performance, stable blue MR‐TADF emitters for next‐generation UHD display.