Luminous Efficacy of Light Emitting Diode with SrS∶Eu2+ and SrAl2O4∶Eu2+，Dy3+ Long Afterglow Phosphors

doi:10.19894/j.issn.1000-0518.240411

Chinese Journal of Applied Chemistry ›› 2025, Vol. 42 ›› Issue (5): 701-711.DOI: 10.19894/j.issn.1000-0518.240411

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Luminous Efficacy of Light Emitting Diode with SrS∶Eu²⁺ and SrAl₂O₄∶Eu²⁺，Dy³⁺ Long Afterglow Phosphors

Xian-Zhi CHU¹^,², Ran PANG², Song-Lin HAN², Li-Hong JIANG², Hui-Min LI², Xiao-Dong LI¹(), Su ZHANG²(), Hong-Jie ZHANG²

^1.School of Materials Science and Engineering，Jilin Architecture University，Changchun 130118，China
^2.State Key Laboratory of Application of Rare Earth Resources，Changchun Institute of Applied Chemistry，Chinese Academy of Sciences，Changchun 130022，China

Received:2024-12-16 Accepted:2025-04-18 Published:2025-05-01 Online:2025-06-05
Contact: Xiao-Dong LI,Su ZHANG
About author:zhangsu@ciac.ac.cn
lxdjlju@163.com；
Supported by:
the National Key R&D Program of China(2019YFA0709100)

Abstract

Abstract:

Light-emitting diode （LED） sources have become the primary choice for modern lighting systems. To address the flicker issue caused by alternating current （AC） power supplies in LED devices， the use of afterglow materials to mitigate flickering has emerged as a key area of research. However， the optoelectronic performance of LED devices encapsulated with afterglow materials has yet to be systematically investigated. In this study， SrS∶Eu2? and SrAl?O?∶Eu2?，Dy3? afterglow phosphors were synthesized via a high-temperature solid-state reaction， both of which can be efficiently excited by blue light， yielding red emission at 621 nm and green emission at 518 nm， respectively. By encapsulating these phosphors with a 450 nm blue LED chip， and fine-tuning the phosphor-to-encapsulation resin ratio， LED devices with luminous efficacy reaching 130 lm/W and a color rendering index exceeding 85 were achieved. These devices meet the requirements for general white-light illumination， underscoring the promising application prospects of long-afterglow phosphors in LED lighting technology.

Key words: Afterglow phosphors, Light-emitting diode, Luminous efficacy, Color rendering index

CLC Number:

O611.4

Xian-Zhi CHU, Ran PANG, Song-Lin HAN, Li-Hong JIANG, Hui-Min LI, Xiao-Dong LI, Su ZHANG, Hong-Jie ZHANG. Luminous Efficacy of Light Emitting Diode with SrS∶Eu²⁺ and SrAl₂O₄∶Eu²⁺，Dy³⁺ Long Afterglow Phosphors[J]. Chinese Journal of Applied Chemistry, 2025, 42(5): 701-711.

Figures/Tables 16

Fig.1 XRD patterns of the series of samples of SrS∶0.04Eu2+ （A） and SrAl2O4∶0.04Eu2+，0.01Dy3+（B）

Fig.2 The SEM diagrams and the morphology-related element mapping of the SrS∶0.04Eu2+

Fig.3 The SEM diagrams and the morphology-related element mapping of the SrAl2O4∶0.04Eu2+，0.01Dy3+

Fig.4 （A） Diffusive spectra of SrS∶0.04Eu2+；（B） Diffusive spectra of SrAl2O4∶0.04Eu2+，0.01Dy3+

Fig.5 Excitation and emission spectra of SrS∶0.04Eu2+

Fig.6 Excitation and emission spectra of SrAl2O4∶0.04Eu2+，0.01Dy3+

Table 1 Different proportions of epoxy resin and SrAl2O4∶0.04Eu2+，0.01Dy3+ phosphor

Serial number	m（epoxy resin）/g	m（phosphor）/g	m（phosphor）∶m（epoxy resin）
1	0.5	0.05	1︰10
2	0.5	0.10	1︰5
3	0.5	0.15	3︰10
4	0.5	0.20	2︰5
5	0.5	0.30	3︰5
6	0.5	0.50	1︰1
7	0.5	0.60	6︰5
8	0.5	0.80	8︰5
9	0.5	1.00	2︰1
10	0.5	1.50	3︰1

Fig.7 （A） The luminous efficacy and color rendering index of LEDs encapsulated with SrAl2O4∶0.04Eu2?，0.01Dy3? phosphor at different mass ratios of phosphate to adhesive；（B） The luminous efficacy and color rendering index of LEDs encapsulated with SrS∶0.04Eu2? phosphor at different ratios of phosphate to adhesive

Table 2 Different proportions of epoxy resin and SrS∶0.04Eu2+ phosphor

Serial number	m（epoxy resin）/g	m（phosphor）/g	m（phosphor）∶m（epoxy resin）
1	0.5	0.05	1︰10
2	0.5	0.10	1︰5
3	0.5	0.15	3︰10
4	0.5	0.20	2︰5
5	0.5	0.30	3︰5
6	0.5	0.50	1︰1

Fig.8 （A） The emission spectra of LEDs encapsulated with SrAl2O4∶0.04Eu2?， 0.01Dy3? phosphor at different mass ratios of phosphate to adhesive；（B） The CIE coordinates of LEDs device

Fig.9 （A） The emission spectra of LEDs encapsulated with SrS∶0.04Eu2? phosphor at different mass ratios of phosphate to adhesive；（B） The CIE coordinates of LEDs device

Table 3 LED light sources encapsulated with different phosphor-to-epoxy resin ratios

Serial number	m（SrAl₂O₄）/g	m（SrS）/g	m（S525）/g	m（HR-629H）/g
1	1	0.01	/	/
2	3	0.04	0.5	0.02

Fig.10 （A） Spectral comparison of LEDs encapsulated with SrAl2O4∶0.04Eu2?，0.01Dy3? and SrS∶0.04Eu2? phosphors （inset shows the source illuminated and unilluminated）；（B） The chromaticity coordinates of the light source plotted on the CIE chromaticity diagram

Table 4 Optical performance test data for LED light sources with various phosphor-to-epoxy resin ratios

Serial number	Luminous efficacy/（lm·W^-1）	CIE x	CIE y	Ra^*
1	132.68	0.273 1	0.315 1	86.2
2	142.6	0.302 6	0.320 3	96.4

Fig.11 Spectra of LEDs encapsulated with SrAl2O4∶0.04Eu2?，0.01Dy3?， SrS∶0.04Eu2?， and commercial phosphors （inset shows the source illuminated and unilluminated）；（B） The chromaticity coordinates of the light source plotted on the CIE chromaticity diagram

Fig.12 （A） Flexible LED film and Photograph of the AC LED device in operation； Flicker characteristics of the alternating current LED device with LED film （B） and without LED film （D） at 50 Hz； Flicker characteristics of the AC LED device with LED film （C） and without LED film （E） at 400 Hz

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Luminous Efficacy of Light Emitting Diode with SrS∶Eu²⁺ and SrAl₂O₄∶Eu²⁺，Dy³⁺ Long Afterglow Phosphors

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