Substitutional‐Interstitial Synergetic Solid Solution Enables Efficient Ultra‐Broadband Emission and Multicolor Luminescence

ABSTRACT Divalent europium‐activated phosphors have been a remarkable family due to coordination field‐closely dependent multicolor luminescence characteristics. However, achieving efficient ultra‐broadband white emission has been a great challenge. Herein, we report a Eu‐activated ultra‐broadband Ba 5 P 6 O 20 phosphor with a full width at half maximum of up to 209 nm, coming from the multiple‐site occupancy of Eu 2+ . Unfortunately, the internal quantum efficiency (IQE) is as low as 23%. Subsequently, the substitutional solid solution of Gd 3+ for Ba 2+ effectively promotes the reduction Eu 3+ to Eu 2+ and improves the IQE to 88%. The interstitial solid solution of Mg 2+ regulates the Eu 2+ occupancy sites, resulting in an additional emission centered at 407 nm. Finally, simultaneously dissolving Gd 3+ and Mg 2+ ions into Ba 5 P 6 O 20 further improves the IQE (up to 94%) of the ultra‐broadband emission. The incorporation of the studied ultra‐broadband emitting phosphor with 365 nm LED chips realizes a high color rendering index warm white light output. Additionally, benefiting from the interstitial solid solution of Mg 2+ , the resulting material demonstrates promising static/dynamic anti‐counterfeiting performance. This work establishes a substitutional‐interstitial synergistic solid solution engineering, offering valuable insights for highly efficient ultra‐broadband emission and multicolor luminescence of europium.