Insight into Structure, Regulatable Photoluminescence of Stably Self and Codoped Phosphor Ba₃Y₂B₆O₁₅: Dy/Eu for <i>n</i>UV <i>w</i>LEDs

Abstract The exploitation of borate‐based phosphors is garnered tremendous attention in w LEDs. Although previous research provided some insights into borates from the viewpoints of synthesis, structure, and defect evolutions, their photoluminescence (PL) with dopants is still insufficient for actual application, especially on aspects of efficiency/stability. Herein, to alleviate the above issues, a new type of lesser‐known high symmetry Ba 3 Y 2 B 6 O 15 (BYB) codoped with Dy 3+ /Eu 3+ phosphors are synthesized via multistep solid‐state reaction and possessed controllable PL based on n UV excitation, defect‐induced (self‐) PL, and energy transfer (ET) from Dy 3+ to Eu 3+ . The origin of blue self‐PL is clarified based on oxygen‐related defects and optimized via adjusting synthetic atmosphere (air/Ar) and (co)doping dopants to control the defect content. Thanks to dense connectivity, and highly symmetric structure with perfectly ordered octahedral sites of Y 3+ for accommodation of Dy/Eu and ET, “cool” white and red PL from Dy 3+ and Eu 3+ , respectively, show high PL efficiency with narrow full width at half the maximum (fwhm). The phosphor also exhibits excellent thermal stability because of high bandgap and low electron‐phonon coupling. Finally, a high‐quality phosphor‐converted w LED (pc‐ w LED) device is assembled via remote “capping” packaging by adopting the BYB: Dy/Eu and a 350 nm n UV LED chip.