基于量子阱/量子点共振能量转移机制的高效率白光LED的研究

Recently white light-emitting-diode (LED)-based solid-state lighting is commanding much attention worldwide for its promise of energy savings. The predominant white LED technology under investigation involves the employment of high quantum efficiency blue GaN LEDs and down conversion of blue radiation to yellow/green and red for white light generation by phosphor. However, a number of limits on the performance of those white LEDs due to the phosphor-conversion scheme employed, such as short lifetime,low energy tranfer efficiency etc..Recently, quantum dots (QDs) have been introduced to the white LED technology as a new family of phosphor materials to overcome the defail of the phosphor systerm.This project intends to research on the the direct coupling energy transfer mechanism between the InGaN quantum well and CdSe/(Zn,Cd)S quantum dots.The factors impact on the energy tranfer efficiency such as radiative recombination lifetime of InGaN well, distance between the QW and QDs and distribution of QDs will be researched. Two kinds of high-efficiency white LEDs ( Planar QW-QD LED and Sidewall QW-QD LED respectively)with energy-coupled QD-phosphors will be designed and fabricatinged.Benefit from the high efficiency energy tranfer systerm, the fluorescent conversion efficiency and luminous efficiency will reach to 80% and 160 lm/W respectively. This work is targeted at breaking the bottleneck of the low conversion efficiency of white LEDs and greatly promoting the application of LED in solid-state-lighting.

随着节能意识和需求的逐步提高，白光LED固态照明在全世界都得到广泛的关注和发展。目前白光LED主要采用高效率蓝紫光LED激发荧光粉转化为黄、绿和红光混合得到白光，然而基于荧光粉转化的白光LED存在着易老化、转化效率低、色温偏低等诸多缺点。而采用量子点替代荧光粉作为下转换材料具有转换效率高、稳定性和显色性好等优点。本项目拟在研究InGaN量子阱和CdSe/(Zn,Cd)S量子点之间的荧光共振能量转移机理的基础上，深入探讨InGaN量子阱辐射复合寿命、量子点与量子阱的间距、量子点分布方式等因素对能量转移效率的影响，设计并制备具有谐振腔的平面型和侧墙型两种高效的量子点白光LED， 测试并优化白光LED的性能，使其能量转换效率达到80%以上，发光效率达到160lm/W，显色指数达到85以上。本项目的研究有望突破白光LED系统中光色转换效率低下的瓶颈，促进白光LED在照明领域的应用。

随着节能意识和需求的逐步提高，白光LED固态照明在全世界都得到广泛的关注和发展。目前白光LED主要采用高效率蓝紫光LED激发荧光粉转化为黄、绿和红光混合得到白光，然而基于荧光粉转化的白光LED存在着易老化、转化效率低、色温偏低等诸多缺点。而采用量子点替代荧光粉作为下转换材料具有转换效率高、稳定性和显色性好等优点。本项目首先通过在蓝光LED芯片表面直接涂覆量子点和硅胶混合物的方式，研究了多种颜色的量子点配比对白光LED发光效果的影响，在绿色:黄色:红色CdSe/ZnS量子点质量配比为5:2:1的条件下制备了光效为118lm/W、显色指数为88.6的量子点白光LED。在此基础上，设计了纳米孔阵列型量子点白光LED的器件结构及工艺路线，采用Lloyd干涉曝光技术和ICP干法刻蚀技术在GaN基蓝光LED外延片表面制备了孔径和周期均为250nm，且穿透p-GaN直到量子阱有源层的纳米孔阵列，然后在纳米孔阵中旋涂不同浓度和配比的CdSe/ZnS量子点制得纳米孔阵列型量子点白光LED。结果表明：当量子点比例为最佳配比时，得到了显色指数为91.7的白光LED，其最佳光效为93lm/W，色坐标为（0.3681,0.3547），色温为4203K，接近自然光。这种白光LED的显色指数达到了91.7的最高值，远远高于普通的荧光粉白光LED（显色指数小于75），达到了优良级别，这将为量子点白光LED在显示屏背光源领域的应用提供有力的推动并将促进量子点作为荧光转换材料在白光LED中应用。