Blue Multiple‐Resonance Thermally Activated Delayed Fluorescence Materials

Abstract Organic light‐emitting diodes (OLEDs) exhibit significant advantages in the fields of ultra‐high‐definition (UHD) displays and wearable devices. However, developing low‐cost, high‐efficiency, and high‐purity blue emission materials remains a significant challenge for academia and industry. While thermally activated delayed fluorescence (TADF) materials meet low‐cost manufacturing needs and achieve 100% internal quantum efficiency, their charge‐transfer excited states lead to broad emission spectra that don't meet the BT.2020 standard. Fortunately, the multiple resonance (MR) strategy offers an effective solution for creating blue TADF materials with high color purity. Through careful structural design and precise tuning of excited state energy levels, blue MR‐TADF materials can easily achieve a full‐width at half‐maximum (FWHM) of less than 30 nm. Nevertheless, it still faces significant challenges, such as severe aggregation‐induced quenching and efficiency roll‐off. Herein, this work overviews the recent progress of blue MR‐TADF materials and devices, and introduce representative molecular design strategies aimed at suppressing concentration quenching, enhancing reverse intersystem crossing rates, and achieving deep blue emission, which will aid future endeavors to develop more efficient, stable blue MR‐TADF materials and devices suitable for UHD display applications.