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Highly efficient inorganic phosphors are crucial for solid-state lighting. In this paper, a new method of low-temperature self-reduction was used for preparing a highly efficient deep blue-emitting phosphor of Ca[B 8 O 11 (OH) 4 ] : Eu 2+ (CBH : Eu 2+ ). The crystal structure, morphology, chemical state, and photoluminescence (PL) properties of the CBH : Eu 2+ phosphor have been investigated. By using the screened hybrid function (HSE06), the band gap (E g ) of CBH was calculated to be 7.48 eV, which is a necessary condition for achieving high quantum yield phosphors. The experiment results show that almost all the added raw materials of Eu 3+ can be reduced to Eu 2+ in CBH crystal under a non-reducing atmosphere. The CBH : Eu 2+ phosphor shows a broad excitation spectrum centered at 277 and 327 nm in the range of 220 to 400 nm, and a narrow-band emission spectrum centered at 428 nm in the range of 400 to 500 nm, with a full width at half maximum (fwhm) of 42.35 nm. Under UV radiation, the CBH : 2 %Eu 2+ exhibits high photoluminescence quantum yield (PLQY=95.0 %), high external quantum efficiency (EQE=31.1 %), and ultra-high color purity (97.6 %). The PL intensity of CBH : 2 %Eu 2+ remains 62.6 % of the initial intensity at 150 °C. Finally, the white light-emitting diodes (WLED) fabricated by CBH : 2 %Eu 2+ , excited by a 365 nm chip, presents outstanding performances with a luminous efficacy (LE) of 13.9 lm/W, a color rendering index (CRI) of 89.4, and a correlated color temperature (CCT) of 5825 K. The above results show that CBH : Eu 2+ can be used as a promising blue phosphor for WLED. This new method of low-temperature self-reduction can be applied to design and prepare other new types of highly efficient phosphors., (© 2021 Wiley-VCH GmbH.)

A highly efficient blue-emitting phosphor of Sr[B 8 O 11 (OH) 4 ]:xEu 2+ was synthesized though a medium-high temperature boric acid melting method by means of a self-reduction mechanism. The quantum yield and color purity of Sr[B 8 O 11 (OH) 4 ]:6%Eu 2+ are both as high as 99%. The PL intensity of Sr[B 8 O 11 (OH) 4 ]:6%Eu 2+ at 150 °C remains 84% of that at 25 °C.