Bright Red-Emitting Ca₃LuAl₃B₄O₁₅:Ce³⁺,Sm³⁺ Phosphors with High Thermal Stability for Elevating the Color Rendering of Near-Ultraviolet-Based White-Light-Emitting Diodes

The important objectives that have been usually ignored regarding the development of white-light-emitting diodes (WLEDs) are the stability, red spectral region deficiency, high correlated color temperature (CCT), and low color-rending index (CRI) that restrict their effectiveness for practical implementation. Herein, we used systematic screening of multi-doped Ca₃LuAl₃B₄O₁₅ (CLAB) samples to evaluate singly and doubly doped down-converting phosphors that exhibit tuning emission and spectrally pure red emission with high color purity at the ultraviolet light excitation and enhanced thermal stability. A comprehensive kinetic model of the energy transfer (ET) mechanism was developed and validated with the extensive experimental data set. Applying this model, we elucidated the ET mechanisms producing a spectrally pure red emission via dipole–dipole interaction. Moreover, CL_0.8AB:0.1Ce³⁺,0.1Sm³⁺ revealed excellent chemical stability under 80% relative humidity and 80 °C severe thermal conditions. Interestingly, when the temperature was increased from 300 to 425 K, the intensity of Ce³⁺ emission was reduced with the production of certain Sm³⁺ emissions via ET. The WLED containing CL_0.8AB:0.1Ce³⁺,0.1Sm³⁺ and Sr₂SiO₄:Eu²⁺ demonstrated warm white light with a high CRI of 89.8–85.7 and a low CCT equal to 4393–4482 K. These parameters are comparable to that of the commercially available YAG:Ce³⁺ phosphor combined with a blue LED chip (CCT ≈ 7746 K and CRI ≈ 75).