TiO2微粒对远程荧光粉膜及白光发光二极管器件光色性能的影响

利用热压法将TiO₂微粒掺入至YAG:Ce荧光粉和硅树脂中制备出远程荧光粉膜并封装成白光发光二极管(LED)器件, 通过荧光粉相对亮度仪、双积分球测试系统和可见光光谱分析系统对样品的光色性能及机理进行了研究. 结果表明: TiO₂的散射效应能够显著提高蓝光的利用率和黄光的透射强度, 白光LED器件的光通量在TiO₂浓度为0.966 g/cm³ 时达到最高值415.28 lm(@300 mA, 9.3 V), 提高了8.15%, 相关色温从冷白6900 K逐渐变化至暖白3832 K. TiO₂的掺入不仅提高了远程荧光粉膜的发射强度和白光LED器件的光通量, 同时能调控其相关色温.     

Design optimization of broadband extreme ultraviolet polarizer in high-dimensional objective space

With the purpose of designing the extreme ultraviolet polarizer with many objectives, a combined application of multi-objective genetic algorithms is theoretically proposed. Owing to the multi-objective genetic algorithm, the relationships between different designing objectives of extreme ultraviolet polarizer have been obtained by analyzing the distribution of nondominated solutions in the four-dimensional objective space, and the optimized multilayer design can be obtained by guiding the searching in the desired region based on the multi-objective genetic algorithm with reference direction. Compared with the conventional method of multilayer design, our method has a higher probability of achieving the optimal multilayer design. Our work should be the first research in optimizing the optical multilayer designs in the high-dimensional objective space, and our results demonstrate a potential application of our method in the designs of optical thin films.     

基于远程荧光技术的高显指白光LED的制备和性能研究

针对目前LED灯具在照明方面显色性不足,以及传统LED点胶封装所存在的芯片发热导致荧光粉性能衰减、色温漂移、出光不均匀等问题,采用近年来新兴的远程荧光封装方式。用黄绿色YGG荧光粉和氮化物红色荧光粉,与硅胶制成远程荧光片封装成LED灯具。通过大量实验确定了黄绿粉、红粉与硅胶的最佳比例,制备了不同色温的LED灯具,并选择了色坐标,光效,显色指数,R9,色质指数,色温,全色域指数等参数对灯具进行了测试与分析,为优质LED照明提供了更客观地综合评价。实验结果表明红粉与黄绿粉的最佳比例为1∶7.6,荧光粉总量与硅胶最佳比例为1∶5,此时制成的白光LED灯具的色温为4 113 K,色坐标(x, y)为(0.375 4, 0.373 1),光效为52.33 lm·w-1,色域度为0.981,显色指数高达96,其中R9为97。色质指数Qa值高达93,全色域指数为79。同时相较于传统封装而言,远程荧光封装的荧光板表面温度大大低于点胶封装荧光粉表面温度,可以有效地避免温度过高对LED产生的不良影响。     

Theory of multiphoton photoemission disclosing excited states in conduction band of individual TiO2 nanoparticles

A theory of multiphoton photoemission is derived to explain the experimentally observed monotonic decrease with the wavelength in the electron yield of TiO₂ nanoparticles (NPs) by as large as four orders of magnitude. It is found that the fitting parameter corresponds to the energy position of Ti3d e_g and t_2g states, and the derived theory is a novel diagnostic of excited states in the conduction band, very importantly, applicable to individual NPs. The difference between four-photon slope NPs and three-photon slope NPs is attributed to the difference in defect density. The success of the theory in solving the puzzling result shows that thermal emission from high-lying levels may dominate over direct multiphoton ionization in solids when the photon number larger than four is required.     

低密度SnO2靶激光等离子体极紫外光及离带热辐射

极紫外光刻技术是我国当前面临35项“卡脖子”关键核心技术之首.高极紫外光转换效率和低离带热辐射的激光等离子体极紫外光源是极紫外光刻系统的重要组成部分.本文通过采用激光作用固体Sn和低密度SnO₂靶对极紫外光源以及其离带热辐射进行研究.实验结果表明,两种形式Sn靶在波长为13.5 nm附近产生了强的极紫外光辐射.由于固体Sn靶等离子体具有较强自吸收效应,在光刻机中心工作波长13.5 nm处的辐射强度处于非光谱峰值位置.而低密度SnO₂靶具有较弱的自吸收效应,其所辐射光谱的峰值恰好位于13.5 nm处.相比于固体Sn靶,低密度SnO₂靶中处于激发态的Sn离子发生跃迁所产生的伴线减弱,使其在13.5 nm处的光谱效率提升了约20%.另一方面,开展了极紫外光源离带热辐射(400—700 nm)的实验研究,光谱测量结果表明离带热辐射主要是由连续谱所主导,低密度SnO₂靶中含有部分低Z元素O(Z=8),导致其所形成的连续谱强度低,同时离带辐射时间短,因而激光作用低密度SnO₂靶所产生的离带...