From Nonluminescence to Bright Blue Emission: Boron-Induced Highly Efficient Ce³⁺-Doped Hydroxyapatite Phosphor

Photoluminescence quantum efficiency (QE) and thermal stability are important for phosphors used in phosphor-converted light-emitting diodes (pc-LEDs). Hydroxyapatite, Ca₅(PO₄)₃OH, is generally not used as host for phosphors, because the OH^- group in the host will lead to a high vibrational frequency around the activators and reduces the luminescent efficiency or even quenches the emission. In this work, strong blue emission at 450 nm appears after introducing boron atoms into Ce³⁺-doped hydroxyapatite under excitation of a UV light. Analyses suggest that B atoms enter into the host structure, which lead to the modification of crystal structure and the formation of vacancies of O and H to compensate charge mismatch. The decrease of OH^- groups around Ce³⁺ ion on Ca (3) site is responsible for the appearance of strong blue emission. The absolute QE value of the best blue-emitting phosphor is ∼92%, and the emission intensity at 150 °C remains 81% of that at room temperature. The emission peak and International Commission on Illumination (CIE) coordinates hardly change upon increasing temperature. The results suggest that boron-modified hydroxyapatite phosphor could be a candidate for UV-LED-pumped white phosphor-converted LEDs. This strategy may provide a new insight into the exploration of phosphors' hosts and other functional materials.