Tailoring of Blue‐Cyan Luminescence in Rb₃Y[(P_1‐<i>_x</i>Si<i>_x</i>)O₄]₂:Eu²⁺ Phosphor via Si⁴⁺‐P⁵⁺ Heterovalent Substitution for Full‐Spectrum Healthy

Abstract Filling the cyan gap (470–500 nm) in white light‐emitting diodes (WLEDs) is crucial for full‐spectrum illumination. However, the traditional approach of adding cyan phosphor to red, green, and blue phosphors can lead to reabsorption and color aberrations due to spectral overlap and varying degradation rates among the mixed phosphors. Herein, a blue‐cyan‐emitting phosphor (λ em = 475 nm) is developed through Si 4+ ‐P 5+ heterovalent substitution in blue‐violet‐emitting Rb 3 Y(PO 4 ) 2 :Eu 2+ phosphor (λ em = 425 nm), which can serve as the blue component in WLEDs to fill the cyan gap without adding extra phosphor. Initially, Eu 2+ primarily occupy the Rb2O 12 sites (426 nm) in Rb 3 Y(PO 4 ) 2 :Eu 2+ , with minimal occupation in the Rb1O 7 sites (456 nm) and YO 6 sites (522 nm). The Si 4+ ‐P 5+ substitution results in a red‐shift of the Eu 2+ @Rb1 emission peak from 456 to 475 nm and the preferred occupation of the Rb1 sites by Eu 2+ , synergistically achieving the blue‐cyan luminescence. Employing the blue‐cyan‐emitting phosphor instead of the blue‐violet‐emitting phosphor in WLEDs significantly improves the color rendering index from 90 to 97.2, thus enhancing the overall color reproduction quality. This research demonstrates a facile composition modification method to modulate the properties of inorganic luminescent materials and provides an alternative solution for full‐spectrum healthy lighting.