Guo-Juan Wang,Qiang-Qiang Zhu,Gan-Yu Cai,Yue Zhai,Shuang-Qiang Fang,Juan Kang,Le Wang
The realization of high-quality laser-driven white light remains challenging due to the limited heat dispersion and inconsistent light uniformity of color converters. In this study, ZnO particles with high thermal conductivity and a high index of refraction were induced into phosphor-in-glass (PiG) films to form a Y 3 Al 5 O 12 (YAG):Ce 3+ -ZnO composite structure. The influences of ZnO particles on the luminescence, optical properties, thermal dissipation performance, and light uniformity of PiG films were studied in detail. Benefiting from the improved thermal dissipation, the luminescence saturation threshold of the YAG:Ce 3+ PiG film was improved from 10.97 to 12.96 W/mm 2 , and the luminous flux was improved from 1271 to 1468 lm. The increased light scattering attributed to ZnO particles also effectively dispersed both laser and emitted light. This significantly enhanced the angular consistency of the color rendering index (Ra) and correlated color temperature (CCT). It indicates that the YAG:Ce 3+ -ZnO composite PiG film would be an interesting color converter for producing high-quality laser-driven white light.
Laser-driven white lighting sources promise super-high brightness, good directionality and high efficiency, but are usually suffering from low color rendering index (Ra), high correlated color temperature (CCT) and poor light uniformity. To solve these problems, we designed bi-color phosphor-in-glass (PiG) films containing broadband green and red phosphors, and introduced Al 2 O 3 particles as scattering centers into the PiG films. The addition of Al 2 O 3 effectively increases the Ra value from 83 to 93, and greatly improves the angular uniformity in Ra and CCT with C v (Ra) decreasing from 14.96% to 0.16% and C v (CCT) decreasing from 45.87% to 1.5%. The coefficient of variation (C v ) is used to evaluate the light uniformity, and the smaller the value, the better the uniformity. The color temperatures can be tuned in a wide range of 2500 ∼ 6300 K by controlling the content of Al 2 O 3 or the ratios of phosphor-to-glass in the films as well as their thicknesses, while high Ra values of > 90 are maintained. A prototype laser-driven white light with excellent color qualities (Ra = 95, Rf = 95, Rg = 104, R9 = 99, R15 = 98) and a high luminous efficacy of 102 lm/W was demonstrated for stage spotlights by optimizing the composition and structure of the bi-color PiG films. This work highlights the roles of secondary phase in heat dissipation and light scattering, and provides ideas to design PiG color converter films for use in super-high color quality laser lighting.
Fluorescent glass shows promising applications in solar cell covers with high mechanical properties and effective wavelength conversion. By high-temperature feeding melting-pouring-annealing integration synthetic technique, (58-x)B 2 O 3 -25La 2 O 3 -8.5CaO-3.5ZnO-3SiO 2 -xTb 4 O 7 (x = 2–9 mol%) glass was fabricated to examine the impact of Tb 4 O 7 concentration. These glasses exhibited high thermal stability (T g > 670 °C), along with excellent optical properties, including a refractive index >1.7 and transmittance reaching 85%. The fluorescent properties optimized through excitation spectroscopy, emission spectroscopy, fluorescence lifetime measurement and auxiliary XPS testing, which demonstrated that 3 mol % Tb concentration of sample yielded the most favorable results. Micro-area fluorescence testing revealed that the coefficient of variation of the fluorescence intensity integral was 1.65%, indicating the sample had decent fluorescence uniformity. These results provided important guidance for the design of fluorescent glasses with superior service performance and luminescent properties.
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