New Deep-Blue-Emitting Ce-Doped A4-mBnC19+2mX29+m (A = Sr, La; B = Li; C = Si, Al; X = O, N; 0 ≤ m ≤ 1; 0 ≤ n ≤ 1) Phosphors for High-Color-Rendering Warm White Light-Emitting Diodes

Ca[B8 O11 (OH)4 ] : Eu2+ - A Highly Efficient Deep Blue-Emitting Phosphor Prepared by Low-Temperature Self-reduction

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[B₈ O₁₁ (OH)₄ ] : Eu²⁺ (CBH : Eu²⁺ ). The crystal structure, morphology, chemical state, and photoluminescence (PL) properties of the CBH : Eu²⁺ 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 Eu³⁺ can be reduced to Eu²⁺ in CBH crystal under a non-reducing atmosphere. The CBH : Eu²⁺ 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 %Eu²⁺ 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 %Eu²⁺ remains 62.6 % of the initial intensity at 150 °C. Finally, the white light-emitting diodes (WLED) fabricated by CBH : 2 %Eu²⁺ , 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 : Eu²⁺ 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.

Intense emissions in Ce3+/Eu2+ doped Ca5.93-mSrmBa(PO4)4O phosphors via host adjustment and energy transfer

A series of Ca_5.93-m-x-2ySr_mBa(PO₄)₄O:xEu²⁺,yCe³⁺,yLi⁺ (0 ≤ m ≤ 0.5, 0 ≤ x ≤ 0.07, 0 ≤ y ≤ 0.05) phosphors were designed via solid-state reaction method, and the photoluminescence properties were studied for application in white light-emitting diodes (LEDs). When a small amount of Sr²⁺ was introduced into the initial Ca₆Ba(PO₄)₄O host, the solid solution was formed, which was verified by the XRD technique. The Eu²⁺ in the host shows intense yellow emitting light, which can be largely enhanced by incorporating Sr²⁺ in the host. When the Ce³⁺ was doped into the host, blue emission was received under 380 nm excitation, and the optimal Ce³⁺ concentration is for y = 0.04. Very efficient energy transfer (ET) from Ce³⁺ to Eu²⁺ appeared in the Ce³⁺-Eu²⁺ codoped samples, and the yellow emission of Eu²⁺ can be further enhanced by this ET. The thermal-quenching luminescence of the as-prepared samples was evaluated by the temperature-dependent emission spectra, which indicated that the introduction of Sr²⁺ can improve the thermally luminescence stability of Eu²⁺. The fabrication of the LEDs device revealed that the Ce³⁺-Eu²⁺ activated samples in this work could show potential applications in white LEDs.

Thermal stability of nitride phosphors for light-emitting diodes

Improving thermal stability of nitride phosphors has become an important material challenge. Our review describes three thermal phenomena, lists strategies for enhancing thermal stability of nitride phosphors, and discusses prospects in the future.

Pyrophosphate Phosphor Solid Solution with High Quantum Efficiency and Thermal Stability for Efficient LED Lighting

Phosphors with high quantum efficiency and thermal stability are greatly desired for lighting industries. Based on the design strategy of solid solution, a series of deep-blue-emitting phosphors (Sr0.99-xBax)2P2O7:0.02Eu2+ (SBxPE x = 0-0.5) are developed. Upon excitation at 350 nm, the optimized SB0.3PE phosphor shows a relatively narrow full width at half maximum (FWHM = 32.7 nm) peaking at 420 nm, which matches well with the plant absorption in blue region. Moreover, this phosphor exhibits obvious enhancement of internal quantum efficiency (IQE) (from 74% to 100%) and thermal stability (from 88% to 108% of peak intensity and from 99% to 124% of integrated area intensity at 150°C) compared with the pristine one. The white LED devices using SB0.3PE as deep-blue-emitting component show good electronic properties, indicating that SB0.3PE is promising to be used in plant growth lighting, white LEDs, and other photoelectric applications.