含硅氮/氧化物基质白光发光二极管发光材料的研究进展

PROGRESS OF NITRIDOSILICATES PHOSPHORS FOR PHOSPHOR-CONVERSED WHITE LIGHT EMITTING DIODE

白光发光二极管(light emitting diode,LED)应用于常规照明的快速发展需要具有"暖"白光输出的高功率白光LED,而目前常用的氧化物基质发光材料,如:铈掺杂钇铝石榴石(cerium doped yttrium aluminum garnet,YAG:Ce)及Eu2+激活碱土硅酸盐很难满足该要求。因此,发展具有红色发光成分和优越温度特性的发光材料是当务之急。以SiO2,Si2N2O和Si3N4为基本反应单元,它可以与M'2O(M'=碱金属)、MO(M=碱土金属及Zn等)、Re2O3(Re=稀土,Al,B)、M'3N、M3N2、ReN、AlN及BN等反应,生成一系列的硅氮/氮氧化物基质发光材料,如:M'Si2N3,MSiN2,M2Si5N8,MSi2N5,Si3N4·ReN,Si3N4·2ReN,Si3N4·3ReN,Si3N4·6ReN,MReSi4N7,MAlSiN3,Si2N2O·MO,Si2N2O·3MO,Si2N2O·Re2O3,Si2N2O·2Re2O3,Si3N4·2MO,Si3N4·Re2O3,2Si3N4·Re2O3和SiO2·ReN……这些以(Si,Al)(O,N)4四面体为结构基元的硅氮化合物,具有比氧化物更高的化学稳定性及更强的共价性;某些5d→4f跃迁的稀土离子,如:Eu2+,Ce3+和Yb2+,在该基质材料中具有很宽的激发带和高效的长波长发射特性,并且它们的组成可以在很宽的范围变化而不改变其晶体结构,因此可实现从绿色到红色光谱范围的发光,如:氮氧化物可实现黄绿色发光,而纯氮化物可实现红色发光。因而,用该硅氮化合物发光材料封装的白光LED可实现"冷"白到"暖"白光输出,且对温度和驱动电流的变化不敏感,是目前色彩稳定性最高的白光–LED。本文综合评述了近年来硅氮/氮氧化物基质白光LED发光材料的研究结果与最近进展,系统地归纳、总结了硅氮/氮化物基质白光LED发光材料的晶体结构、发光性能、以及应用特性,并分析了目前国际上对该材料的研究动态及应用情况。

High-power white light-emitting diodes （LEDs） with warm white light output are required for the rapid advances in general illumination applications of white LEDs. However, the currently employed oxide phosphors, such as cerium doped yttrium aluminum garnet （YAG：Ce） and Eu^2＋ activated alkaline earth silicate, can hardly meet the challenge; therefore, it is urgent to develop novel phosphors with red-emitting components and excellent temperature-dependent properties. A series of nitridosilicates can be obtained through SiO2, Si2N2O or Si3N4 with M＇2O （M＇= alkali metals）, MO （M=alkaline earth, Zn）, Re2O3 （Re=are earth, Al, B）, M＇3N, M3N2, REIN, AlN, or BN, etc., such as： M＇Si2N3, MSiN2, M2SisNs, MSi2Ns, Si3N4-ReN, Si3N4·2ReN, Si3N4-3ReN, Si3N4-6ReN, MReSi4N7, MA1SiN3, Si2N2O-MO, Si2N2O-3MO, Si2N2O-Re2O3, Si2N2O-2Re2O3, Si3N4·2MO, Si3N4·Re2O3, 2Si3N4-Re2O3, and SiO2·ReN Some of these silicon nitrides/oxynitrides based on （Si, Al）（O, N）4 tetrahedra building units possess higher chemical and thermal stability and stronger covalency than that of the corresponding oxide. Some rare earth ions （such as Eu^2＋, Ce^3＋ and Yb^2＋） with a 5d→4f transition exhibit very broad excitation bands and highly efficient long-wavelength emission characteristics in these silicon nitride/oxynitride hosts. Moreover, the chemical composition can be altered over a broad range without changing the crystal structure, which makes it possible to adjust the emission color and chromaticity from the green region to the red region; for example, yellow-green emission can be realized in silicon oxynitride hosts, and red emission can be achieved in silicon nitride hosts. So cool white to warm white light output can be realized by white LEDs based on these silicate nitride/oxynitride phosphors; furthermore, these white LEDs show the highest color stability with temperature and drive current so far. Recent progress in silicon nitride/oxynitride host luminescent materials with broad excitation bands for phosphor-converted white LEDs are briefly reviewed in this paper, including the crystal structure, spectroscopic properties and application characteristics. We also discuss the application prospects and the trends of research and development of these phosphors.