白光LED用金、银纳米粒子敏化增强碳量子点发光玻璃的研究

The soluble carbon quantum dots with high quantum yield and emitting white light excited by the violet light and blue light will be synthesized by the method of hot injection and pyrolyzation etc. Metal sensitized carbon quantum dots doping sodium borosilicate glass for white LEDs will be prepared via sol-gel method by mixing the precursor solution containing noble metal Au, Ag with the soluble carbon QDs. Then, the as obtained glass is composited with the blue light chip and the violet light chip to prepare white LEDs source. The effect of species and ratio of precursor, surface modifying agent,reaction temperature on the luminescence efficiency of the carbon quantum dots are investigated by absorption spectroscopy, single-photon fluorescence spectroscopy, time-resolved fluorescence technique etc.The pore structure and size distribution of the dry sodium borosilicate gel can be controlled by sintering reaction temperature.The narrow distribution and high concentrations of carbon quantum dots uniformly dispersed in the pore wall can be obtained by varying the type of precursor, sintering reaction temperature,heating rate and holding time, The formation mechanism of metal sensitized carbon quantum dots in the glass is investigated by XRD, SEM, HRTEM. Meanwhile,the effect of the composition, structure, size and the surface states of carbon quantum dots coupling with metals on luminous efficiency, color temperature, color rendering index, decay of white LED light source are studied. Finally, the light emitting mechanism of carbon quantum dots is created combined with the theoretical model, and the noble metal Au, Ag sensitized carbon quantum dots doping sodium borosilicate glass for white LEDs could be grow controllably.

本项目采用热注入和热解等方法制备在紫光和蓝光激发下能发射白光且量子产率高的水溶性碳量子点，与分别含有Au和Ag的先驱体溶液混合，用溶胶-凝胶法制备含有金属敏化增强白光发射碳量子点钠硼硅玻璃，分别与蓝光芯片和紫光芯片复合制备出白光LED光源。采用吸收光谱、单光子荧光光谱技术、时间分辨荧光技术、变温荧光光谱等技术研究前驱体的种类、比例、反应温度、表面修饰剂等因素对碳量子点白光发光效率的影响；通过调节先驱体的种类、升温速率、保温时间调控干凝胶微孔结构尺寸分布，在孔壁中形成具有单分散、高浓度、均匀掺杂的碳量子点；采用XRD、SEM、HR-TEM等手段研究金属敏化碳量子点在玻璃中的形成机理；研究碳量子点组成、结构、尺寸以及表面态与金属的耦合关系对白光LED光源的光效、色温、显色指数、光衰等光学性质的影响，结合理论模型计算，建立碳量子点的发光机制；实现金属敏化增强碳量子点在玻璃中的可控生长。

本项目主要采用热注入法制备碳量子点（碳点），通过选择合适的碳源及表面功能化修饰剂，获得高发光效率的碳点，系统研究了表面功能化碳点的合成制备条件以及碳点浓度对发光性能的影响。通过调节碳点的浓度实现了发射波长从530 nm至620 nm的发光可调，借助FT-IR、TEM、HRTEM、XPS等表征手段对碳点的微结构、尺寸及形貌进行了深入分析，详细探讨了碳点的发光机理。.其次，采用溶胶凝胶法制备了碳量子点钠硼硅凝胶（CDs-NBS）玻璃，所掺杂的碳点浓度最高可达70%。经透射电子显微镜图像分析可知CDs-NBS凝胶玻璃中碳量子点分布均匀，分散性良好。随着碳点掺杂浓度的增加，其荧光发光峰出现了明显的红移现象而且量子效率明显增强。我们将发黄光的CDs-NBS凝胶玻璃与蓝光GaN基LED芯片相结合制备了碳点复合白光LED器件，得到白光LED器件的最优色坐标为（0.32，0.33），显色指数为78.9，光效为58.1 lm/W。.此外，本项目详细研究了Au 、Ag等金属离子对碳点发光性能的影响。研究发现调节Au、Ag纳米粒子和碳量子点的比例可实现碳点荧光不同程度的敏化，获得了最大荧光增强倍数。并进一步对Au、Ag敏化碳量子点复合材料颗粒尺寸、形貌、微结构及发光特性等进行分析表征，探讨了Au、Ag敏化碳点发光原理。.我们还研究制备了N掺杂全光谱碳量子点，通过调节控制碳点表面修饰基团氮、氧含量，可在469~658nm之间调节发射峰的位置，采用流延法和丝网印刷等方法制备了碳点夹层荧光玻璃，并应用紫光激发的全光LED。这些夹层荧光玻璃样品的色坐标图呈现出一种线性分布，其发射光颜色分别为红、橙、黄、白、蓝绿、蓝和深蓝，所得的白光LED器件的色坐标CIE为（0.32，0.33），非常接近于纯白光的色坐标CIE（0.33，0.33）。碳量子点发光材料的优异性能有望成为下一代白光LED的备选材料。