Bright Red-Emitting Ca<sub>3</sub>LuAl<sub>3</sub>B<sub>4</sub>O<sub>15</sub>:Ce<sup>3+</sup>,Sm<sup>3+</sup> Phosphors with High Thermal Stability for Elevating the Color Rendering of Near-Ultraviolet-Based White-Light-Emitting Diodes
Wasim Ullah Khan, Wasim Ullah Khan, Waheed Ullah Khan, Waheed Ullah Khan, Hao Lin, Zhiyuan Cheng, Muhammad Wajid Shah, Yueli Zhang
Abstract
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, CL0.8AB: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 CL0.8AB: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).