摘要
随着发光材料的研发和半导体制作工艺的改进,白光半导体发光二极管(LED)的发展非常迅速,它已经趋向取代传统的照明,由于白光LED具有的长寿命、无污染、低功耗的特性,未来LED还将逐步替代荧光灯、白炽灯成为下一代绿色照明光源。
本论文首先简单介绍LED的概念、特点、提出了现阶段白光LED存在的问题:即发光效率的提高和导热问题的解决。针对白光LED所存在的问题,提出新型光热复合材料——量子点/荧光粉复合材料的合成及复合导热材料的开发。
1、以氯化镉、硒氢化钠为前驱体,采用超声水浴法制备水溶性CdSe量子点并使用紫外吸收光谱与荧光光谱、透射电子显微镜等测试其光学性质和形貌结构。研究结果表明制得的量子点尺寸为2-3nm,通过改变反应时间、反应温度、反应溶液的pH值、稳定剂的浓度及反应物的摩尔配比等条件,可以得到不同发光波长和强度的CdSe量子点。最终将量子点发光材料掺杂到LED荧光粉中。制备高发光效率的复合发光材料的研究有待进一步的开展。
2、散热的研究。由于PN结温度的上升会使发光复合的几率下降,发光二极管的亮度就会下降,寿命和输出光通也会随着温度的升高而下降,如果PN结产生的热量能尽快的散发出去,不仅能提高产品的发光效率,同时也能提高产品的可靠性和寿命。因此研究一种高导热复合材料可以大大提高LED的工作性能。
With the development of material and the innovation of semiconductor manufacture technology,the rapid development of white LEDs is more and more significant.White LEDs have tended to replace the traditional lighting,owing to their long life,non-polluting,low-power performance.LEDs will open a new era in "green lighting".
The paper first briefly introduces the concept and characteristics of LEDs. Currently,white LEDs are confronted with two problems of low luminescent efficiency and bad heat dissipation.To solve the above problems,the investigation in novel luminescent and thermal composite materials is performed in this paper.
1、Water-soluble cadmium selenide(CdSe) QDs by employing CdCl_2 and NaHSe as precursors were synthesized in alkaline aqueous solution by ultrasonic method.Their structure and optical properties were studied by photoluminescence spectroscopy,UV-Vis spectra and transmission electron microscope.The result showed that the size of CdSe QDs was about 2-3nm and their optical properties such as the wavelength and intensity of photominescence were dependent on the reaction time,the growth temperature,the pH value,the concentration of stabilizing agent and reactants etc.Eventually quantum dots were doped into the LED light-emitting phosphors and further study is to be carried out.
2、Another aspect is the heat dissipation.In general,the cooler the environment,the higher an LED's light output will be.Higher temperatures generally reduce light output and LED's lifetime.If the heat within the junction is dissipated by convection and conduction,the actual lifetime and the efficiency of LED would be increased.Nano-composite materials with high thermal conductivity have been explored to enhance the LED performance.
引文
[1]Barton DanielL,Osinski Marek,Perlin Piotr,etal.Life tests and figure mechanisms of GaN/A1GaN/InGa Nlighting Emitting Diodes[A].SPIE[C],1998,3279:17-27
[2]Adachi,S.Model Dielectric Constants of GaP,GaAs,SaSb,InP,InAs,InSb.Physical Review B,1987,35:7454-7463
[3]Linnik,M.,and A.Christou.Calculations of Optical Properties for Quantemary Ⅲ-Ⅴ Semiconductor Alloys in the Transparent Region and Above(0.2-4.0 eV).Physica,2002,318(3):140-161
[4]J.K.Sheu,J.M.Tsai,et al.Low-Operation Voltage of InGaN/GaN Light-Emitting Diodes With Si-Doped In_(0.3)Ga_(0.7)/GaN Short-Period Superlattice Tunneling Contact Layer.IEEE Electron Device Letters,2001,22(10):460-462
[5]Steigerwald,D.A.Illumination with Solid State LightingTechnology.IEEE J.on Selected Topics on Quantum Electronics,2002,8(7):310-320
[6]Delbeke.High Efficiency Semiconductor Resonant-cavity Light-emitting iodes:A Review.IEEE J.on Selected Topics on Quantum Electronics,2002,8(2):189-206
[7]Danielas,Jeromecb,Davec,etal.Illumination with solid state lighting echnoloy.IEEE JonSelected Topicsin Quantum Electronics,2002,8(2):310-320
[8]刘行仁,黄德森,薛胜薛等.白光现状和问题.光源与照明,2003,3:4
[9]魏茂林,齐鸣,李爱珍.横向过生长(LED)外延GaN材料及其生长机理.功能材与器件学报,2001,7(2):199-205
[10]曲宝壮等.新工艺生长的InGaN量子点的结构与电学性质研究.功能材料与器件学报,2003,9(1):13-16
[11]Optical Dispersion Relations for GaP,GaAs,SaSb,InP,InAs,InSb,AlxGal-xAs,and Inl-xGaxAsyP1-y.J.Appl.Phys.,1989,66:6030-6040
[12]关兴国.AlGaInP红橙黄光高亮度LED外延材料.半导体情报,2000,37(6):50-54
[13]Nakamura S.A bright futurefor blue/green LEDs[J].IEEE Circuits &Devices,1995,11(3):19-223
[14]林秀华.白光LED器件可靠性初探.全国LED产业研讨会与学术会议论文集,2002.15-17
[15]张雷,李冬光.填充型高分子复合材料导热性能研究[J].郑州大学学报(理学版),2006,38(1):105-109
[16]周文英,齐暑华,涂春潮,等.绝缘导热高分子复合材料研究[J].塑料工业,2005,33(21):99-102
[17]李冰,张晓伟.环氧树脂导热复合材料的研究进展[J].Z中国胶粘剂,2008,17(1):60-62
[18]储九荣,张晓辉,徐传攘.导热高分子材料的研究与应用[J].高分子材料科学与工程,2000,16(4):17-21
[19]杨海涛,魏伯荣,闫刚,等.高分子材料热导率影响因素分析[J].塑料工业,2005,33(10):1-4
[20]S E Gustafsson,E Karawacki,M A Chohan..J.Phys.D:Appl.Phys.,1986,19:727-7351
[21]杜洛金(美)原编著,奚同庚编译。固体热物理性质导论,北京:中国计量出版社,1987,42
[22]S E Gustafsson,E Karawacki,M N Khan.J.Phys.D:Appl.Phys.,1979,12:1411-1421
[23]Murray,C.B.;Norris,D.J;Bawendi,M.G.Journal of the American Chemical Society 1993,115:8706-8715
[24]Talapin,D.V.;Rogach,A.L;Kornowski,A.;Haase,M.;Weller,H.Nano Letters,2001,1:207-211
[25]L.H.Qu,X.G.Peng,Z.A.Peng.Alternative Routes toward High Quality CdSe Nanocrystals[J].Nano.Lett.2001,1:333-337
[26]Y.W.Cao,U.Banin.Growth and Properties of Semiconductor Core/Shell Nanocrystals with InAs Cores[J].J.Am.Chem.Soc.2000,122:9692-9702
[27]G.Nikolai,V.Dmitri,H.Weller.Thiol-Capping of CdTe Nanocrystals:An Alternative to Organometallic Synthetic Routes[J].J.Phys.Chem.B.2002,106:7177-7185
[28]L.Spanhel,M.Haase,H.Weller,A.Henglein.Photochemistry of Colloidal Smiconductors Surface Modification and Stability of strong Luminescing CdS Particles[J]J.Am.Chem.Soc.1987,109:5649-5655
[29]M.Y.Gao,S.Kirstein,H.Mohwald,A.Rogach,A.Kornowski,A.Eychmuller,H.Weller. Strongly Photoluminescent CdTe Nanocrystals by Proper Surface Modification[J].J.Phys.Chem.B.1998,102:8360-8363
[30]H.B.Bao,Y.J.Gong,Z.Li,M.Y.Gao.Enhancement Effect of lumination on the Photoluminescence of Water-Soluble CdTe Nanocrystals:Toward Highly Fluorescent CdTe/CdS Core-Shell Structure[J].Chem.Mater.2004,16:3853-3859
[31]谢颖,徐静娟,于俊生,陈洪渊.水溶性的CdSe/ZnS纳米微粒的合成及表征[J].无机化学学报,2004,20:663-667
[32]H.F.Qian,C.Q.Dong,J.F.Weng,J.C.Ren.Facile One-Pot Synthesis of Luminescent,Water-Soluble and Biocompatible Glutathione-Coated CdTe Nanocrystals[J].Small,2006,15:747-751
[33]H.Zhang,Z.Zhou,B.Yang,M.Y.Gao.The Influence of Carboxyl Groups on the Photoluminescence of Mercaptocarboxylic Acid-Stabilized CdYe Nanoparticles[J].J.Phys.Chem.B.2003,107:8-13
[34]Ivan Sondi,Olavi Siiman.Synthesis of CdSe nanoparticles in the presence of aminodextran as stabilizing and capping agent.Journal of Colloid and Interface Science,275,(2004):503-507
[35]C.Petit,M.P.Pileni,Physical properties of self-assembled nanosized cobalt particles,Applied Surface Science,2000,162-163:519-528
[36]Quinlan F T,Kuther J,Stroeve P,etal.Reverse Micelle Synthesis and Characterization of ZnSe Nanoparticles.Langmuir,2000,16(8):4049-4051
[37]Meyer F,Dierstein A,Beck Ch,et al.Size-controlled synthesis of nanoscaled aluminium spinels using heterobimetallic alkoxide precursors via water/oil microemulsions.Natostructured Materials,1999,12(1):71-74
[38]Qiu S P,Dong J X,Chen G X.Synthesis of CeF3 nanoparticles from water-in-oil microemulsions.Powder Technology,2000,113(1):9-13
[39]Li G L,Wang G H.Synthesis of nanometer-sized TiO2 particles by a microemulsion method.Nanostructured Materials,1999,11(5):663-668
[40]J.J.Zhu,Y.Koltypin,A.Gedanken.General Sonochemical Method for The Prepraration of Nanophasic Selenides:Synthesis of ZnSe Nanoparticles[J].Chem.Mater.2000,12:73-78.
[41]R.Katoh,Y.Tasaka,E.Sekreta,etal.Sonochemical Production of a Carbon Nanotube[J].Ultrason Sonochem.999,64:185-187
[42] M.Mdlelent, T.Hyeon, K.S.Suslick.Sonochemical Synthesis of Nanostructured Molybdenum Sulfide [J].J Am.Chem.Soc.l998,120:6189-6190
[43] Zuo J, Xu C Y, Liu X M, etal. Study of the Raman spectrum of nanometer SnO. J App Phys, 1994, 75(6): 1835-1838
[44] Chen W, Wang Z G, Lin Z J, etal. Absorption and luminescence of the surface states in ZnS nanoparticles. J Appl Phys, 1997, 82(6): 3111-3116
[45] Nirmal M, Murray C B, Bawendi M G Fluorescence-line narrowing in CdSe quantum dots: Surface localization of the photogenerated exciton. Phys Rev B, 1994,50(4): 2293-2300
[46] Henglein A. Small-particle research: physicochemical properties of extremely small colloidal metal and semiconductor particles. Chem Rev, 1989,89(10):1861-1873
[47] Vogel R, Hoyer P, Weller H. Quantum-sized PbS, CdS, Ag_2S, Sb_2S_3, and Bi_2S_3particles as sensitizers for various nanoporous widebandgap semiconductors. J Phys Chem, 1994, 98(12): 3183-3188
[48] Peng X G, Alivisatos A P. Epitaxial growth of highly luminescent CdSe/CdS core/shell nanocrystals with photostability and electronic accessibility. J Am Chem Soc, 1997, 119(14):7019-7029
[1]陈异,高濂.胶体法制备CdSe纳米晶,无机材料学报,2002,17(4):1289-1291
[2]Lifshitz E,Dag I,Litvin I,et al.Optical properties of CdSe nanoparticle films prepared by chemical deposition and sol-gel methods.Chem Phys Lett[J],1998,288(2,3,4):188-196
[3]Dongsheng Xu,Xuesong Shi,et al.Electrochemical Preparation of CdSeNanowire Arrays.J.Phys.Chem.B,2000,104:5061-5063
[4]Li Yadong,Liao Hongwei,etal.Room Temperature Synthesis of Metal Chalcogenides in Ethylenediamine.Inorg,Chem,1999,38(7):1382-1387;
[5]任国兰,柴宜民,卫洪青.量子点荧光探针的合成[J].山西师范大学学报(自然科学版),2003,17(1):60-62
[6]王璐,王德平.水相制备硒化镉半导体量子点的荧光性能.硅酸盐学报,2005,33(10):1224-1230
[7]WOGGON U.Optical properties of semiconductor quantum dots[J].Springer Tracts in Modern Physics,1996,136:245-249
[8]H.Y.Han,Z.H.Sheng,J.G.Liang.A Novel Method for The Preparation of Water-solube and Small-size CdSe Quantum Dots[J].Mater.Lett.2004,60,3782-3785
[9]L.H.Qu,X.G.Peng,Z.A.Peng.Alternative Routes toward High Quality CdSe Nanocrystals[J].Nano.Lett.2001,1:333-337
[10]B.S.Zou,R.B.Little,J.P.Wang,M.A.ElSayed.Effect of Different Capping Environments on The Optical Properties of CdS Nanoparticles in Reverse Micelles[J].Intl.J.Quantum.Chem.1999,72,439-450
[11]Dongzhi Yang,Qifan Chen,Shukun Xu.Synthesis of CdSe/CdS with a simple non-TOP-based route.Journal of Luminescence.2007(126):853-858
[12]E.Jang,S.Jun,Y.S.Chung.etal.Surface Treatment to EnhanceTthe Quantum Efficiency of Semiconductor Nanocrystals[J].J.Phys.Chem.B,2004,108,4597-4600
[13]Kayanuma Y.Quantum-size effects of interaction electrons and holes in semiconductor micrystals with spherical shape[J].Phys Rev,1988,B38:9797-9805
[14]孙平,王引书,颜其礼等.CdS_(0.1)Se_(0.9)半导体纳米晶体的生长和吸收光谱研究[J].北京师范大学学报(自然科学版).2000,36,184-197
[15]师昌绪,李恒德,周廉.材料科学与工程手册[M].北京,化学工业出版社,2004,10-39,10-90
[16]J.N.Demasa,G.A.Crosby.The Measurement of Photoluminescence Quantum Yields.A Review[J].J.Phys.Chem.1971,75,991-1023
[1]李侃社,王琪.导热高分子材料研究进展[J].功能材料,2002,33(2):136-144
[2]Sugimoto Toshio,Kawaguchi Sadahiko.[P].Jpn Kokai Tokkyo Koho,JP06157718,1994
[3]丁峰,谢维章.导热树脂基复合材料[J].复合材料学报,1993,10(3):19-24
[4]吕瑞涛,黄正宏,康飞宇.高导热炭基功能材料研究进展材料导报2005,10(5):45
[5]井新利,李立匣.石墨-环氧树脂导热复合材料的研究[J].西安交通大学学报,2000,34(10):106-110
[6]张晓辉,徐传骧.新型电力电子器件封装用导热胶粘剂的研究[J].电力电子技术,1999(5):61-62
[7]Sim LC,Ramanan SR,Ismai LH.Thermal character-ization of Al_2O_3and ZnO reinforced silicone rubber as ther-mal pads for heat dissipation purposes[J].Thermochimia Acta,2005,430(1-2):155-165
[8]黄祖洪,周健.高导热多胶粉云母带研制过程中的几个问题[J].绝缘材料,2003(3):10-12
[9]沈源,傅仁利,何洪,等.氮化硅/环氧复合电子基板材料制备及性能[J].热固性树脂,2007,22(1):16-35
[10]张洁,王炜,曾宪华.氮化铝颗粒增强聚合物基板材料的制备及介电性能研究[J].航空材料学报,2006,26(3):341-342
[11]Xu Y S,Chung D D L,Mroz C.Thermally conducting aluminum nitride polymer-matrix composites[J].Composites,Part A:applied science and manufacturing,2001,1:749-1757
[12]周文英,齐暑华,赵红振,等.复合绝缘导热胶粘剂研究[J].中国胶粘剂,2006,15(11):22-25
[13]刘阳,孟晓玲.高导热型铝基覆铜箔板的研制[J].覆铜板资讯,2007(2):26-29
[14]S.Berber,Y.-K.Kwon,D.Tomanek:Unusally high thermal conductivity of carbon nanotubes,Phys.Rev.Lett.84,4613(2000)
[15]M.Fujii,X.Zhang,H.Q.Xie,et al:Measuring the Thermal Conductivity of a Single Carbon Nanotube,Phys.Rev.Lett.95,065502(2005)
[16]P.Kim,L.Shi,A.Majumdar,P.L.McEuen:Thermal transport measurements of individual multiwalled nanotubes,Phys.Rev.Lett.87,215502(2001)
[17] M. J. Biercuk, M. C. Llaguno, M. Radosavljevic, et al: Carbon nanotube composites for thermal management, Appl. Phys. Lett. 80, 2767 (2002)
[18] S. U. S. Choi, Z. G Zhang, W. Yu, et al: Anomalous thermal conductivity enhancement in nanotube suspensions, Appl. Phys. Lett. 79,2252 (2001)
[19] S.V. Kidalov, F.M. Shakhov, A.Ya. Vul. Thermal conductivity of nanocomposites based on diamonds and nanodiamonds [J]. Diamond & Related Materials 16 (2007) 2063-2066
[20] S.V. Kidalov, F.M. Shakhov, A.Ya. Vul. Thermal conductivity of sintered nanodiamonds and microdiamonds[J]. Diamond & Related Materials 17 (2008)844-847
[21] Lee GW, Lee JI, Lee SS, etal. Comparisons of thermal properties between inorganic filler and acid-treated multiwall nanotube/polymer composites [J]. Journal of materials science 40 (2005) 1259 - 1263
[22] Xu Y, Ray G, Abdel-Magid B, Thermal behavior of single-walled carbon nanotube polymer-matrix composites, Compos Part A 2006;37:114-121