Achieving High Light Uniformity Laser-driven White Lighting Source by Introducing Secondary Phases in Phosphor Converters

doi:10.15541/jim20220074

Abstract

Abstract:

Laser-driven white lighting sources have great potential for applications with super-high brightness, high directionality and long distance illumination, but are usually limited by their poor uniformity due to mismatch between blue laser light and phosphor converted light. In this work, a secondary phase of TiO₂, BN, Al₂O₃ or SiO₂ was introduced as scattering media in the Y₃Al₅O₁₂: Ce³⁺ (YAG) phosphor-in-glass (PiG) film to regulate the light path, where the optimum concentration of the secondary phase was determined, respectively. The images of illumination and speckle, angular distributions of luminance and color temperature, as well as optical properties of the white light produced by the different secondary phases based-YAG PiG films were investigated. The light uniformity in luminance and color temperature is greatly improved by introducing secondary phases, among which TiO₂ is demonstrated as the best one as it has the largest relative reflective index. In addition, the YAG-TiO₂ PiG film has the largest luminance saturation threshold of 20.12 W/mm² and the highest luminous flux of 1056.6 lm under blue laser irradiation. This work paves an avenue to choose appropriate scattering media in PiG films for realizing more uniform and brighter laser-driven white lighting source.

Key words: light uniformity, laser-driven white lighting source, scattering, phosphor-in-glass film, optical properties

CLC Number:

O482

DENG Taoli, CHEN Hexin, HEI Lingli, LI Shuxing, XIE Rongjun. Achieving High Light Uniformity Laser-driven White Lighting Source by Introducing Secondary Phases in Phosphor Converters[J]. Journal of Inorganic Materials, 2022, 37(8): 891-896.

Figures/Tables 12

Fig. S1 CCT (a) and illuminance (b) distribution curves at different angles (10°~170°) of YAG PiG films with different TiO2, BN, Al2O3, or SiO2 contents

Table S1 CCT uniformity of YAG PiG films with different TiO2, BN, Al2O3, or SiO2 contents under blue laser excitation

Uni_CCT/%	0	10%	15%	20%	25%	30%
TiO₂	10.4	91.5	94.3	94.8	91	91
BN	10.4	73.6	86.9	88.4	94.1	90.9
Al₂O₃	10.4	18.1	-	84.2	-	89.3
SiO₂	10.4	12.1	13.7	19.4	16.2	48.3

Fig. 1 (a-e) Cross-section and (f-j) top-view SEM images of (a, f) YAG, (b, g)YAG-TiO2, (c, h) YAG-BN, (d, i) YAG-Al2O3, (e, j) YAG-SiO2 PiG films; (k-o) SEM image of the selected area of the YAG-TiO2 PiG film and corresponding EDS mappings of Y, Al, Ca and Ti

Fig. S2 Photoluminescence spectra and lifetime of YAG, YAG-TiO2, YAG-BN, YAG-Al2O3, YAG-SiO2 PiG films

Fig. 2 (a-e) Illumination images of laser-driven white light sources from YAG, YAG-TiO2, YAG-BN, YAG-Al2O3, and YAG-SiO2 PiG films under excitation of a laser power density of 1.72 W/mm2, and (f-j) Speckle images of YAG, YAG-TiO2, YAG-BN, YAG-Al2O3, and YAG-SiO2 PiG films under 445 nm laser excitation

Table 1 Luminance uniformity of YAG-based PiG films with different scattering media

Sample	None	SiO₂	Al₂O₃	TiO₂	BN
$\bar{x}$/(Mcd·m^–2)	0.51	0.25	0.22	0.12	0.11
σ	1260	554	461	248	205

Fig. 3 (a) Luminance of light spots in YAG, YAG-TiO2, YAG-BN, YAG-Al2O3, and YAG-SiO2 PiG films under excitation with a laser power of 0.015 W, respectively, (b) luminance distribution curves along the light spot diameter, and (c) photograph of the light spot at a distance of 10 m when the YAG-BN PiG film pumped by a blue LD

Fig. 4 (a) CCT and (b) illuminance distribution curves at different angles (10°-170°) of YAG, YAG-TiO2, YAG-BN, YAG-Al2O3, and YAG-SiO2 PiG films

Table 2 CCT uniformity of YAG, YAG-TiO2, YAG-BN, YAG-Al2O3, YAG-SiO2 PiG films under blue laser excitation

Sample	None	SiO₂	Al₂O₃	BN	TiO₂
Max/K	100000	50780	6720	7124	6620
Min/K	4745	6798	5193	5287	5073
Ave/K	45565	14080	5815	5621	5353
Uni/%	10.4	48.3	89.3	94.1	94.8

Table 3 Relative refractive indexes of secondary phases introduced into the YAG-PiG film

	SiO₂	Al₂O₃	BN	TiO₂
n₂	1.48	1.76	1.73	2.61
R	0.000045	0.0064	0.0051	0.073

Fig. 5 (a) Quantum efficiency and absorption efficiency, (b) luminous flux, and (c) luminous efficacy of YAG, YAG-TiO2, YAG-BN, YAG-Al2O3, and YAG-SiO2 PiG films

Fig. S3 Temperatures of light spots of YAG, YAG-TiO2, YAG-BN, YAG-Al2O3, YAG-SiO2 PiG films

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