Excited‐State and Steric Hindrances Engineering Enable Fast Spin‐Flip Narrowband Thermally Activated Delayed Fluorescence Emitters with Enhanced Quenching Resistance

) values exceeding 30 % with suppressed efficiency roll-offs and improved operational stability. This work offers an effective approach for designing doping-insensitive blue and green MR-TADF materials with fast spin-flip processes by integrating the engineering of excited states and steric hindrances.