白光LED用荧光玻璃陶瓷的发光性能研究
文献类型：学位论文
| 作者 | 李杨 |
| 文献子类 | 博士 |
| 导师 | 胡丽丽 |
| 关键词 | 荧光玻璃陶瓷 Color Conversion Glass Ceramic 白光LED White Light-emitting Diode 量子效率 Quantum Yield 可靠性性能 Reliability Property 散热性能 Heat Dissipation Property |
| 其他题名 | Study on photoluminescence properties of color conversion glass ceramics for white light-emitting diodes |
| 英文摘要 | 白光LED（Light-Emitting Diode）光源因其节能、环保、长寿命等特点，近年来逐渐取代传统白炽灯被广泛应用于照明和显示等新一代光源中。随着LED芯片技术、荧光粉技术和LED封装技术的不断发展，应用市场对LED的大功率、低色容差、高显色、色温可调等发光性能和可靠性性能要求不断提高。目前，批量生产的白光LED光源，主要采用硅胶将各种色温的荧光粉固化粘接在蓝光芯片上耦合制备获得。通过选择小晶格失配的衬底晶体和不断优化提高GaN镀膜技术，蓝光LED芯片的输出功率显著增长。同时，各种色温荧光粉的发光性能和可靠性性能也显著提高。然而，在LED光源封装中使用的各种硅胶的玻璃转变温度（Tg）只有150℃，LED光源使用时，蓝光芯片产生的热量很容易造成硅胶老化变形，而使得荧光粉和蓝光芯片的白光耦合失效，导致LED的色温漂移。此外，老化变形的硅胶很容易压断蓝光芯片和支架之间连接的金线，使得LED使用可靠性变差。 为了解决硅胶造成的LED光源可靠性问题，各种省去硅胶粘接的荧光材料如荧光晶体，荧光玻璃陶瓷和荧光透明陶瓷被相继研发。荧光晶体，其发光性能优良，但是很难制备大尺寸，价格昂贵，在现有产业化低成本的LED光源上的应用前景有限。荧光透明陶瓷，发光性能没有荧光晶体好，而且低成本大尺寸高透过率的透明陶瓷同样很难制备。荧光玻璃陶瓷，尤其是现阶段发展较快的phosphor-in-glass（PIG）技术，将玻璃粉和市场成熟的各种荧光粉混合二次烧结，发光性能接近于各种荧光粉，可靠性性能部分高于荧光粉，避免了硅胶的使用，其热淬灭性能和热导率性能相较于荧光粉硅胶有显著提高，可显著改善硅胶造成的LED光源可靠性问题。在各种荧光玻璃陶瓷研究中，按照玻璃的构成组分，主要分为低烧结温度的碲酸盐荧光玻璃陶瓷和高稳定性的硼硅基质荧光玻璃陶瓷。碲酸盐荧光玻璃陶瓷，因其烧结温度较低，最大程度避免了二次烧结中高温和玻璃基质的氧化环境对荧光粉性能的影响，其玻璃熔液粘度小，容易制备出各种尺寸发光性能较好的样品。但是，碲酸盐基质性能不稳定，在混合烧结红绿荧光粉时，容易与荧光粉发生反应，使得荧光粉彻底失去了发光性能。硼硅基质荧光玻璃陶瓷，烧结温度较高，玻璃熔液粘度大，较难获得各种尺寸的发光性能好的荧光玻璃陶瓷。但是，硼硅基质性能稳定，可以混合烧结各种红色，绿色和黄色荧光粉，这在各种色温及高显色的LED光源封装中非常重要。现有产业化的LED光源，就是通过各种色温的荧光粉耦合蓝光芯片，满足不同的色温、色容差等发光参数的需求。硼硅基质荧光玻璃陶瓷，在稳定性和低成本方面的优势，使其在LED光源封装方面有较好的应用前景。 本论文共包含六个部分。 第一章为文献综述部分，首先介绍了白光LED光源的发光原理和封装结构，荧光粉的发光原理和封装局限性，继而讨论了荧光玻璃陶瓷的研究现状，从而提出本文研究内容及思路。 第二章主要介绍了荧光玻璃陶瓷样品的制备方法和性能测试。 第三章系统研究了常用的LED可调波长红色和绿色荧光粉，主要包含：绿粉GaYAG和LuAG，红粉Eu:CaAlSiN的发光性能和可靠性性能研究。绿粉0.06Ce:Y 0.06Ce:Y0.06Ce:Y 2.942.942.942.94(Al (Al1-xGa x)5O12 ，在黄粉YAG（钇铝石榴石）的基础上通过Ga取代Al，x值从0.15增加到0.35，荧光粉的发光中心波长从545nm 蓝移到525nm，同时Ga取代降低了荧光粉的热稳定性和可靠性性能。绿粉Lu2.94-xYxAl5O12:0.06Ce (x=0,0.2,0.4,0.6和0.8)，随着Y含量从0增加到0.8，绿粉的发射峰值波长从520nm红移到540nm，当Y取代Lu含量增加到0.4，LuAG晶格中没有出现YAG相时，荧光粉获得了最好的热稳定性和可靠性性能。可调波长的氮化物红粉SrxCa1-xAlSiN3: 0.05Eu2+（x=0.2,0.35,0.5,0.65,0.8），随着Sr含量的增加，荧光粉的发射波长蓝移，荧光粉的量子效率和热稳定性增强，但是耐湿性能和抗水解性能减弱。 第四章系统研究了单掺的黄粉YAG、可调绿粉GaY和LuAG，以及可调红粉Eu:CaAlSiN 硼硅基质荧光玻璃陶瓷的烧结性能、发光性能和可靠性性能。通过对硼硅基质玻璃粉和荧光粉混合二次烧结性能研究发现，随着烧结温度的增加，荧光粉因发光中心稀土离子被玻璃基质氧化，或荧光粉晶格结构被玻璃熔液腐蚀破坏等作用而逐渐失去发光性能，通过在还原气氛下或在低温下烧结，可获得较好发光性能的荧光玻璃陶瓷。对比分析了荧光粉和对应的荧光玻璃陶瓷的发射光谱，量子效率，晶格结构、热稳定性和可靠性性能，发现低温650℃以下烧结时，硼硅玻璃基质基本没有改变荧光粉的发射光谱、晶格结构、热稳定性和可靠性性能，但是所制备的荧光玻璃陶瓷的量子效率还需提高。 第五章首先研究了复合掺杂荧光粉玻璃陶瓷的发光性能。然后，对比测试分析了，采用荧光粉硅胶、荧光薄膜和荧光玻璃陶瓷封装的COB（Chip On Board）型 LED光源的光通量、光效、色温等发光性能和散热性能。发现，制备的荧光玻璃陶瓷，因为量子效率不高，发光性能对大电流瞬态的稳定性弱于荧光粉硅胶和荧光薄膜，但是，在大电流持续点亮一段时间后，因为散热性能好，比荧光粉硅胶的长期使用可靠性好，PN结结温测试也显示了，荧光玻璃陶瓷的PN结结温低于荧光粉硅胶结构。 最后是论文的结论部分，总结了全文的实验结果，同时指出本研究存在的不足和需要进一步研究之处。; White light-emitting diodes (WLEDs) have been widely used in the new generation of light source such as luminescence and display in recent years instead of traditional incandescent lamps due to their being low energy consumption, environmentally friendly and long lifetime features. With the continuous developments of LED chips, phosphors and LED encapsulation technologies, demands of LEDs with high power, low color tolerance, high color rendering, color temperature adjustable and high reliability performances are increasing. The current commercial WLEDs commonly use epoxy resin or silicone to combine blue chips with phosphors. The output power of blue chip has increased significantly due to the small lattice mismatched substrate and continuous improvement of GaN coating technology. Meanwhile, the luminescence properties and reliability performances of phosphors with various color temperature have also been significantly improved. However, the glass transition temperature of the silica gel used in the LED is only 150℃. When the LED is lighting, the heat produced by the blue chip can easily cause the aging deformation of the silica gel, which would cause the light coupling of the phosphor and blue chip to fail, resulting in the color temperature drift. In addition, aged and deformed silica gel can easily break the gold wire between the blue chip and the bracket, which would degrade long term reliability of LED. In order to solve the reliability problem of LED light source caused by silica gels, various fluorescent materials, such as crystals, glass ceramics and transparent ceramics have been developed to instead of phosphors with silica gel. Although fluorescent crystals have excellent luminescence properties, it is difficult to apply to present industrial LEDs because of their difficulty in preparing large scale and high price.The luminescence properties of fluorescent transparent ceramics are slightly worse than that of fluorescent crystals, and it is also difficult to prepare high transmittance ceramics with low cost and large size. The color conversion glass ceramics, especially phosphor-in-glass ceramics which are prepared by cosintering the mixture of glass frits and various phosphors, have as good luminescence properties as phosphors, can significantly improve the reliability of LED due to their good heat quenching performance and thermal conductivity by omitting silica gel. In the present study of various color conversion glass ceramics, according to the composition of glass frits, it is mainly divided into tellurite glass ceramics with low sintering temperature and borosilicate glass ceramics with high stability. For the tellurite powders, two advantages are favorable for their use: one is low sintering temperature against the reaction between the glass powders and phosphors to keep the original properties of phosphors; the other is low viscosity of melting glasses which can prepare various sizes of glass ceramics to encapsulate LED light sources easily. Unfortunately, when tellurite glass frits are cosintered with some green and red phosphors, it is easy to destroy the luminescence properties due to the reactions between phosphors and glasses. The borosilicate powders are hard to be prepared various shapes of glass ceramics due to their high sintering temperature and viscosity of melting, but they are stable for commercial yellow, green and red phosphors which is very important to encapsulate LED with various color temperature and high color rendering index. It is through the coupling of blue chips with various color temperature phosphors, present commercial LEDs can achieve the requirement of different color temperature, low tolerance and other luminous parameters. Because of the advantages of stability and low cost, borosilicate glass ceramics have good application prospects in the field of LED encapsulation. This study includes the following six chapters. In chapter 1, literature review has been introduced. Firstly, the principle and packaging structure of white light LED light source and phosphor have been introduced briefly, and then the research status of color conversion glass ceramics was discussed. Finally, the purpose and research content of the dissertation were proposed. In chapter 2, the preparation methods and performance tests for color conversion glass ceramics have been introduced. In chapter 3, the luminescence and reliability properties of the tunable wavelength red and green phosphors such as Ga:YAG, LuAG and CaSiAlN were studied. For 0.06Ce: Y2.94(Al1?xGax)5O12 (x = 0.15–0.35) phosphors, PL emission peaks were shifted from 545 nm to 525 nm after Ga ions had replaced Al ions. Meanwhile, the investigations showed that the addition of Ga can deteriorate the reliability properties of the phosphors. For Lu2.94-xYxAl5O12:0.06Ce (x=0-0.8) phosphors, PL emission peaks were shifted from 520 nm to 540 nm after Y ions had replaced Lu ions. When x was 0.4, the thermal stability and reliability properties of phosphors were best because there is no YAG phase in the lattice. For SrxCa1-xAlSiN3: 0.05Eu2+(x=0.2-0.8) red Abstract VII phosphors, with the increase of Sr content, the emission wavelength of the phosphor were shifted to short wavelength. Meawhile, after Sr ions had replaced Ca ions, the quantum efficiency and thermal stability of the red phosphors were enhanced, but the moisture resistance and hydrolysis resistance were weakened. In chapter 4, the sintering, luminescence and reliability properties of the borosilicate color conversion glass ceramics with single kind of phosphors such YAG, Ga:YAG, LuAG and CaSiAlN were studied. Through the study on the cosintering properties of borosilicate glass frits and phosphors, it was found that low sintering temperature or reduction atmosphere were beneficial for increasing the PL intensity of the color conversion glass ceramics, which could avoid the phosphors losing the luminescence property due to the oxidation of rare earth ions by the glass matrix or the corrosion of the crystal structure of the phosphors by the melting glass. The emission spectrum, quantum efficiency, lattice structure, thermal stability and reliability properties of phosphors and corresponding phosphors glass ceramics were analyzed by contrast. It was found that the borosilicate glass powders had not effect on the emission spectrum, lattice structure, thermal stability and reliability properties of the phosphors when they were cosintered at temperature lower than 650℃. But the quantum efficiency of glass ceramics needs to be improved. In chapter 5, the luminescence properties of the color conversion glass ceramics with multi-chromatic phosphors were studied. Then, the heat dissipation and luminescence properties including luminous flux, luminous efficiency, color temperature of the COB type LED light sources encapsulated by phosphors with silicon gel, luminescent films and the borosilicate conversion glass ceramics have been investigated. The results indicated that the luminescence properties of the LEDs packaged by the conversion glass ceramics were lower than that of the LEDs encapsulated by the other two fluorescent materials when the driving current became larger due to low quantum efficiency of the conversion glass ceramics. But the luminescence properties of the LED encapsulated by the conversion glass ceramics were the best under the same driving current for a long time because of good heat dissipation. The test results of PN junction temperature also showed that the heat dissipation of color conversion glass ceramic was slightly better than the other two kinds of fluorescent materials. In Chapter 6, all results of this dissertation have been concluded. The deficiencies in this work and works needed to be done were pointed. |
| 学科主题 | 材料学 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/31069]  |
| 专题 | 中国科学院上海光学精密机械研究所 |
| 作者单位 | 中国科学院上海光学精密机械研究所 |
| 推荐引用方式 GB/T 7714 | 李杨. 白光LED用荧光玻璃陶瓷的发光性能研究[D]. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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