白光LED用Ce:YAG单晶光学性能及封装工艺的研究

doi:10.3724/SP.J.1077.2014.13481

摘要/Abstract

摘要：

采用提拉法生长了白光LED用Ce:YAG单晶, 通过吸收光谱、激发发射光谱和变温光谱对其光学性能和热稳定性进行了表征, 并研究了晶片用于封装白光LED光源中各因素对其光电性能的影响。Ce:YAG晶片能被466 nm波长的蓝光有效激发, 产生500~700 nm范围内的宽发射带。Ce³⁺的4f→5d轨道的跃迁吸收对应于202、219、247.3、347.4和455.5 nm五个吸收峰, 据此量化分裂的5d能级能量, 依次为21954、29154、40437、45662和49505 cm^-1。温度升高, Ce³⁺的²F_7/2能量升高导致了发光强度的降低, 可降低幅度(13.28%)不大, 比肩国家标准且要优于目前商用白光光源的Ce:YAG单晶制白光LED光源的封装工艺, 从芯片、驱动电流、晶片厚度和添加物四方面进行讨论。研究结果表明, Ce:YAG单晶是一种新型白光LED用荧光材料。

关键词: 白光LED, 铈掺杂钇铝石榴石, 光学性能, 封装工艺, 光电性能

Abstract:

The Ce:YAG single crystal for white light-emitting diode (WLED) application was grown by the Czochralski method. The thermal stability and optical properties of samples were characterized by absorption spectrum, photoluminescence spectra and temperature-dependent PL spectra. The photoelectric performance of WLEDs fabricated by the Ce:YAG single crystal were also measured. It is found that the Ce:YAG single crystal shows a broad emission band from 500 nm to 700 nm under blue light (wave length 466 nm). Absorption peaks, located at 202, 219, 247.3, 347.4 and 455.5 nm, are due to 4f→5d transition, and the energy of 5d orbits is divided into 21954, 29154, 40437, 45662 and 49505 cm^-1. As the temperature increases, the PL intensity is reduced because of a higher energy of the ²F_7/2, and the damping upon PL intensity by the Ce:YAG single crystal (13.28%) are much lower than that by commercially available phosphors (30%). When the current is at a standard state and the luminous flux of emission blue light is around 3.7 lm, the most suitable thickness for the Ce:YAG single crystal is 0.5 mm. Since the WLED fabricated by the Ce:YAG single crystal prepared in present work meets all requirements in related GB codes, and its performance is better in comparison with that of the commercially available one, the Ce:YAG single crystal will possibly be used to fabricate new-type WLED devices.

Key words: WLED, yttrium aluminum garnet doped with Ce, luminescence property, packaging technology, photoelectric property

中图分类号:

O734

向卫东, 赵斌宇, 梁晓娟, 陈兆平, 谢翠萍, 骆乐, 张志敏, 张景峰, 钟家松. 白光LED用Ce:YAG单晶光学性能及封装工艺的研究[J]. 无机材料学报, 2014, 29(6): 614-620.

XIANG Wei-Dong, ZHAO Bin-Yu, LIANG Xiao-Juan, CHEN Zhao-Ping, XIE Cui-Ping, LUO Le, ZHANG Zhi-Min, ZHANG Jing-Feng, ZHONG Jia-Song. Packaging Technologies and Luminescence Properties of Ce:YAG Single Crystal for White Light-emitting Diode[J]. Journal of Inorganic Materials, 2014, 29(6): 614-620.

图/表 11

图1 Ce:YAG单晶制成的白光LED光源(A)和Ce:YAG单晶制得白光LED的封装结构(B)

Fig. 1 A sample of WLED fabricated by Ce:YAG single crystal (A) and Package structure of Ce:YAG single crystal for WLED (B)

图2 Ce:YAG单晶的吸收光谱(A)和插图为MN段谱线用Lorentzian和Gaussian函数分峰拟合的结果(B)

Fig. 2 The absorption spectrum of Ce:YAG single crystal (A) and The inset shows the typical emission of spectrum in MN band separated into Lorentzian and Gaussian distributions (B)

图3 Ce:YAG单晶的激发光谱(A)和发射光谱(B)

Fig. 3 Excitation (A) and emission (B) spectra of Ce:YAG single crystal

图4 Ce:YAG单晶中Ce3+4f和5d的Schematic能级图(A)和Ce3+4f和5d能级的文献值和实验计算值的比较(B)

Fig. 4 Schematic diagram of the energy level and band structure of the 4f and 5d configurations of the Ce3+ ion in a Ce:YAG single crystal field (A) and comparation between the literature values and experimental values of cerium 4f and 5d energy levels (B)

图5 Ce:YAG单晶的变温发光光谱(A)和Ce3+的无辐射跃迁过程(B)

Fig. 5 Temperature-dependent PL spectra of Ce:YAG single crystal (A) and A schematic illustration of nonradiative transition (B)

表1 不同芯片的光电参数

Table 1 Photoelectric parameters of different chips

Samples	Current<br/>/mA	Luminous flux<br/>/lm	Luminous efficacy<br/>/(lm•W^-1)	Colour coordinate (x,y)	Colour temperature<br/>/K
M₁ chip	60	2.687	13.995	0.1540,0.0240	1682
M₂ chip		3.513	18.071	0.1528,0.0268	1665
M₁ chip covered with<br/>epoxy glue		3.689	19.898	0.1552,0.0331	1649
M₂ chip covered with<br/>epoxy glue		3.714	18.533	0.1551,0.0299	1661

图6 Ce:YAG单晶制白光LED用不同芯片在变化的驱动电流下的色坐标

Fig. 6 Colour coordinates of WLEDs fabricated by the Ce: YAG single crystal (z=0.04) and different chips under changeable currents The inset obviously shows the changeable tendency of colour coordinates of WLEDs fabricated by the Ce:YAG single crystal (z=0.04) and different chips under different currents

表2 Ce:YAG单晶制白光LED在不同的驱动电流下的光电参数

Table 2 Photoelectric parameters of WLEDs fabricated by the Ce:YAG single crystal (z=0.04) under changeable currents

Samples	Thick-ness<br/>/mm	Current<br/>/mA	Luminous efficacy<br/>/(lm•W^-1)	Colour coordinate<br/>(x,y)	Colour temperature<br/>/K	Colour-rendering index
WLEDs fabricated by the Ce:YAG single crystal (z=0.04) and M₁ chip	0.5	20	149.028	0.3157,0.3711	6148	66.4
		60	121.466	0.3145,0.3636	6225	67.0
		100	101.316	0.3130,0.3584	6316	67.4
		200	69.415	0.3107,0.3522	6453	67.7
		350	48.643	0.3098,0.3510	6501	68.3
WLEDs fabricated by the Ce:YAG single crystal (z=0.04) and M₂ chip		20	138.617	0.3332,0.4072	5484	63.7
		60	117.950	0.3313,0.3973	5543	64.8
		100	103.093	0.3295,0.3918	5603	65.5
		200	68.295	0.3271,0.3857	5689	66.1
		350	47.530	0.3256,0.3863	5743	67.3

表3 Ce:YAG单晶制白光LED在不同晶片厚度下的光电参数

Table 3 Photoelectric parameters of WLEDs fabricated by the Ce:YAG single crystal (z=0.04) with different thicknesses

Samples	Thickness<br/>/mm	Current<br/>/mA	Luminous efficacy<br/>/(lm•W^-1)	Colour coordinate <br/>(x,y)	Colour temperature<br/>/K	Colour-rendering index
WLEDs fabricated <br/>by the Ce:YAG single crystal (z=0.04) <br/>and M₂ chip	0.4	60	76.744	0.2641,0.2580	15424	75.3
	0.5		91.082	0.3362,0.4113	5395	64.3
	1		91.748	0.3796,0.4934	4547	60.0
	1.5		84.435	0.3772,0.4853	4570	60.7

表4 Ce:YAG单晶制白光LED中添加红粉的光电参数

Table 4 Photoelectric parameters of WLEDs fabricated by the Ce:YAG single crystal (z=0.04) and red phosphors

Samples	Thickness<br/>/mm	Current<br/>/mA	Luminous efficacy<br/>/(lm•W^-1)	Colour coordinate<br/>(x,y)	Colour temperature<br/>/K	Colour-rendering index
1:0.01*	0.5	60	107.765	0.3278,0.3442	5703	74.4
1:0.02*	0.5	60	102.950	0.3378,0.3427	5272	77.7

表5 Ce:YAG单晶制白光LED光源和商业白光LED的光电参数

Table 5 Photoelectric parameters of WLEDs fabricated by eithor Ce:YAG single crystal (z=0.04) or commercial phosphors

Samples	Thickness<br/>/mm	Current<br/>/mA	Luminous efficacy<br/>/(lm•W^-1)	Colour coordinate<br/>(x,y)	Colour temperature<br/>/K	Colour-rendering index
WLEDs fabricated by Ce:YAG single crystal (z=0.04)	0.5	60	107.297	0.3488,0.3580	4862	81.9
Warm-WLEDs fabricated <br/>by phosphors	-	60	103.180	0.3938,0.3850	3730	74.0

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