Absolutely Structural Disorder Boosting Bandwidth toward Full‐Spectrum White Light from Single Occupancy of Activator

Abstract Achieving single‐phase full‐spectrum white light (SFWL) phosphors is a central goal in the optical field because they simplify white‐LEDs assembly and avoid long‐term color instability. Despite many approaches are developed, current SFWL phosphors still suffer from chromaticity drift due to inconsistent thermal quenching of multiple emitting centers. Herein, an absolutely structural disorder strategy is established to develop a single‐emitting center‐based SFWL phosphor. Precisely controlling the flux added induces a structural translation from the absolutely ordered Y 0.75 Ta 0.25 O 1.75 :Bi 3+ to the absolutely disordered Y 0.785 Ta 0.215 O 1.715 :Bi 3+ , as directly identified by STEM‐HAADF analyses. Structural disorder enables Y 0.785 Ta 0.215 O 1.715 :Bi 3+ to produce SFWL with the FWHM of 6194 cm −1 (175 nm) by employing a single activator site, a 1352 cm −1 increase compared to the cyan‐emitting Y 0.75 Ta 0.25 O 1.75 :Bi 3+ despite Bi 3+ occupies two lattice positions. This single‐emitting center‐based SFWL, coupled with minimal thermal expansion of the unit cell and inapparent spectral overlap of excitation and emission bands, ensure zero‐chromaticity shift with elevated temperature. A prototype white‐LEDs using Y 0.785 Ta 0.215 O 1.715 :Bi 3+ as a single luminescent layer generates warm white light without perceptible CIE coordinates shift under various currents or after extremely long‐term continuous operation. This work highlights the potential of structural disorder in designing SFWL phosphors with exceptional color stability.