【作者】 严小松；

【导师】 孙康；

【作者基本信息】 上海交通大学 ， 材料学， 2011， 博士

【摘要】 半导体白光LED光源因其节能、环保、使用寿命长、体积小、反应速度快、耐冲击等诸多优点,被视作人类新一代的光源。本论文从光转换型白光LED发展存在的两个难题——红光区域显色性能不足和多相荧光材料组分之间重吸收出发,通过对适用于455-465 nm蓝光LED芯片和395-405 nm,355-365 nm近紫外光LED芯片的荧光材料进行了研究,具体开展了以下工作:（1） 455-465 nm蓝光芯片激发的YAG:Ce³⁺, Eu³⁺荧光粉利用水热辅助燃烧的合成方法,通过在黄光荧光粉YAG:Ce³⁺中共掺Eu³⁺提高了其红光区域的发射强度,既可避免添加另一相红光材料而造成的重吸收现象,又提高了红光区域的显色性能。结果表明,水热辅助燃烧合成法可以大大降低传统高温固相法所需的反应温度。YAG:Ce³⁺, Eu³⁺荧光粉封装的白光LED弥补了YAG:Ce³⁺荧光粉封装的白光LED在红光区域发射强度不足的缺陷,大幅提高了商业白光LED的显色性能。YAG:Ce³⁺, Eu³⁺荧光粉封装的白光LED在20 mA电流激发下发射出色品坐标（0.3201, 0.3561）,色温为4910K,显色指数82的优质白光,器件的流明效率可达78.71 lm/W。（2） 455-465 nm蓝光芯片激发的CdS:Cu²⁺/ZnS量子点将掺杂量子点作为光转换材料应用于白光LED,以解决多相荧光材料混合后的重吸收问题。通过一锅法合成了发射红光的CdS:Cu²⁺量子点。结果表明,通过控制体系反应的温度从195℃到235℃变化,可以控制CdS:Cu²⁺量子点发射波长从630 nm到710 nm变化。不同掺杂Cu²⁺浓度对CdS:Cu的发射波长影响不大,但可决定CdS:Cu²⁺量子点中CdS本征发射峰与Cu²⁺掺杂发射峰的比例。通过在CdS:Cu²⁺表面包覆ZnS壳层,可以将CdS:Cu²⁺量子效率从18%³0%提高到40%⁵0%,同时提高其光化学稳定性和热稳定性。利用CdS:Cu²⁺/ZnS量子点、YAG:Ce³⁺荧光粉与蓝光LED芯片制成的白光LED,在120 mA驱动电流条件下,可发射出色品坐标为（0.3449, 0.3282）,显色指数86的优质白光,器件的流明效率可达37.43 lm/W。（3） 395-405 nm近紫外芯片激发的CaIn₂O₄:Eu³⁺荧光粉首次合成了物理化学性能更稳定的,能被近紫外光有效激发的新型红光荧光粉CaIn₂O₄:Eu³⁺。通过共掺碱金属离子M+（M=Li,Na,K）,利用M+ + Eu³⁺→2Ca²⁺方式弥补Eu³⁺替位Ca²⁺造成的电荷不平衡,可以大幅提高CaIn₂O₄:Eu³⁺荧光粉的发射强度。通过掺杂Sm³⁺,利用Sm³⁺→Eu³⁺的能量传递,可以拓宽CaIn₂O₄:Eu³⁺荧光粉近紫外区域的激发光谱,并提高CaIn₂O₄:Eu³⁺荧光粉400-405 nm波段的近紫外光的激发强度。（4） 355-365 nm近紫外芯片激发的单一相LiCa₃MgV₃O₍12_:Eu³⁺和SrZn₂（PO₄）₂: Eu²⁺, Mn²⁺白光荧光粉针对近紫外光激发三基色荧光粉材料之间重吸收的问题,研发了近紫外光激发的单一相白光荧光粉体系LiCa₃MgV₃O₍12_:Eu³⁺和SrZn₂（PO₄）₂: Eu²⁺, Mn²⁺。通过高温固相法合成LiCa₃MgV₃O₍12_:Eu³⁺,利用[VO4]3-和Eu³⁺分别对应的发射谱带复合形成白光,通过调节Eu³⁺掺杂浓度,可获得显色性能87,色品坐标（0.33, 0.34）的白光。通过燃烧法合成SrZn₂（PO₄）2:Eu²⁺, Mn²⁺,相比高温固相法合成的样品有更小的颗粒尺寸和更高的发射强度,利用Eu²⁺和Mn²⁺分别对应的发射谱带复合形成白光,通过调节Eu²⁺和Mn²⁺掺杂浓度比例,可获得显色指数为85,色品坐标为（0.35, 0.36）的白光。更多还原

【Abstract】 Due to the long lifetimes, high luminous efficiencies, fast response times, and low power consumptions, solid-state white LEDs have been rapidly growing as a promising option to replace the current illumination applications. In the thesis, two main problems of white LEDs are focused, which are the low color rendering of light in red region and the re-absorption problem among the multi-phased emitting materials. Light converting materials for 455-465 nm blue LED chips and 355-365 nm, 395-405 nm near-UV LED chips were investigated respectively. The main contributions were as follows:（1）Phosphor of YAG:Ce³⁺, Eu³⁺ for 455-465 nm blue LED chipCe³⁺ and Eu³⁺ co-doped YAG phosphor was synthesized by hydrothermal-assist combustion method, and Eu³⁺ was doped to improve the emission light in red region. The sintering temperature of hydrothermal-assist combustion method was much lower than the traditional solid-state method. The emission spectrum of YAG:Ce³⁺, Eu³⁺ was composed of a yellow emission band located at 540 nm corresponding to the characteristic transition of Ce³⁺ and several red emission bands corresponding to the characteristic transitions of Eu³⁺. The fabricated white LED based on blue LED and YAG:Ce³⁺, Eu³⁺ phosphor exhibited a luminous efficiency of 78.71 lm/W, color rendering index （CRI） Ra of 82, and color temperature Tc of 4910K under 20 mA forward bias current.（2）Doped quantum dots （QDs） of CdS:Cu²⁺ for 455-465 nm blue LED chipDoped QDs of CdS:Cu²⁺ were applied in the yellow emitting phosphor of YAG:Ce³⁺ based white LEDs for the first time, not only to complement the absent red component but also to avoid color altering and the decrease of luminous efficiency caused by re-absorption. QDs with emission wavelength ranging from 630 nm to 710 nm can be obtained by controlling the reaction temperature from 195℃to 235℃, and their absorption peak positions and dopant PL peak positions were found to be independent of the Cu²⁺ dopant concentration. By growing a ZnS shell around the CdS:Cu²⁺ QDs, the quantum yields （QYs） of the QDs were observed to increase from 18%³0% to 40%⁵0%, and their photochemical and thermal stabilitieswere also improved. The fabricated white LED based on blue LED chip, YAG:Ce³⁺ phosphor and CdS:Cu²⁺/ZnS QDs exhibited a luminous efficiency of 37.43 lm/W, Ra of 86 under 120 mA forward bias current, and no re-absorption between phosphor of YAG:Ce³⁺ and CdS:Cu²⁺/ZnS QDs was observed.（3）Phosphor of CaIn₂O₄:Eu³⁺ for 395-405 nm near-UV LED chipA novel red emitting phosphor of CaIn₂O₄:Eu³⁺ with high chemical stability and high efficiency under near-UV light excitation was devoloped. By co-doping alkaline metal ions M+（M=Li,Na,K）as charge compensators, the charge imbalanced caused by the doping of Eu³⁺ was compensated in the model of M+ + Eu³⁺→2Ca²⁺, and the emission intensity of the phosphor was greatly improved. Moveover, the absorption intensity of the phosphor of CaIn₂O₄:Eu³⁺ in 400-405 nm near-UV region was enhanced by co-doping Sm³⁺due to the energy transfer from Sm³⁺ to Eu³⁺.（4）Single-phased white emitting phosphors of LiCa₃MgV₃O₍12_:Eu³⁺ and SrZn₂（PO₄）₂: Eu²⁺, Mn²⁺ for 355-365 nm near-UV LED chipSingle-phased white emitting phosphors of LiCa₃MgV₃O₍12_:Eu³⁺ and SrZn₂（PO₄）₂: Eu²⁺, Mn²⁺ for 355-365 nm near-UV excitation were synthesized to overcome the re-absorption problem of the tricolor phosphors. The PL spectra of LiCa₃MgV₃O₍12_:Eu³⁺ showed two emission bands with peaks located at 530 nm and 610 nm, which were attributed to （VO4）3? and Eu³⁺ respectively, and white light with Ra of 87 and coordinate values of （0.33,0.34） was observed with a 10% molar doping concentration of Eu³⁺. Phosphor of SrZn₂（PO₄）₂: Eu²⁺, Mn²⁺ synthesized by combustion method exhibited higher luminous intensity than that synthesized by traditional solid-state method, and blue emission band with peak located at 416 nm from Eu²⁺ occupying the Sr²⁺ site, the green emission band with peak located at 538 nm and the red emission band with peak located at 630 nm from Mn²⁺ occupying two different Zn²⁺ sites were observed in the PL spectra. White light with Ra of 84 and coordinate values of （0.35, 0.36） was obtained by adjusting the ratio of the concentrations of Eu²⁺ and Mn²⁺ properly.更多还原