Spiral‐Locking Strategy for Efficient Narrowband Multiple Resonance Thermally Activated Delayed Fluorescence Emitters

) of up to 32.7%. The referent BNO without spiro skeleton suffers from serious spectral redshift and broadening as well as a lower device efficiency. This research demonstrates a promising approach to developing MR-TADF devices that resist redshift and broadening while maintaining high color purity and efficiency.