NIR LED用新型宽发射带近红外发光材料的设计、合成及机理研究

Currently, the shortage of broad band near infrared (NIR) phosphors matching well with the blue LED chip, especially phosphors with FWHM greater than 250 nm, seriously affects their practical application in many fields, such as the non-destructive detection and analysis of food. In this project, novel broadband NIR phosphors suitable for blue light excitation will be developed. Some compounds with larger cationic coordination number will be selected as host to provide NIR light generation environment for Mn2+, Cr3+, etc. The effective control of the crystal field environment will be realized by adjusting the anion groups, coordination groups and central cations in the host, as the same time, the micro-control mechanism will be studied by using first-principles, and the control scheme is designed to effectively realize and enhance broadband near infrared emission. By using XRD, Refinement and other techniques, the relationship between the host structure and its micro-variation and the luminescent properties of phosphors will be determined. The relationship between the change of band gap and the luminescent properties of phosphors will be investigated by using first-principles calculations and diffuse reflectance spectroscopy etc. The relationship between the persistence characteristic of phosphors and the depth, concentration and distribution of traps will be analyzed in detail. The NIR LED will be fabricated combining with blue LED, and its application value in nondestructive detection of food will be determined by measuring the luminous efficiency and other parameters of the device.

目前适于蓝光LED高效激发的宽发射带近红外发光材料，尤其是半峰宽大于250 nm的材料极为短缺，严重影响了近红外光在食品无损检测及分析等领域的实际应用。本项目致力于研发新型蓝光激发的宽发射带近红外发光材料，尝试选择阳离子配位数较大的化合物作为基质，通过改变基质中阴离子基团、配位基团及中心阳离子等方式，调控Mn2+、Cr3+等发光中心的晶体场强度，同时通过第一性原理研究微观调控机制，辅助设计调控方案，从而有效地实现并增强宽带发射；利用XRD及精修等技术手段研究材料的晶体结构、形貌及配位形式等变化，分析结构及其微变对材料发光性能的影响；利用第一性原理及漫反射光谱等研究基质能带间隙变化与材料发光性能的关系；利用热释光光谱等深入分析材料余辉特性与陷阱深度、浓度以及分布的关系；结合蓝光芯片，构成NIR LED，通过测量器件的发光效率等参数，确定其在食品的无损检测等领域的应用价值。

近红外光在食品无损检测及分析、肿瘤诊断和无创监测人类生理状态等多种领域都表现出了很好的应用前景，目前适于蓝光LED高效激发的宽发射带近红外发光材料，尤其是半峰宽较宽的材料极为短缺，这严重影响了其在上述领域的实际应用。本项目致力于研发新型适于蓝光激发的宽发射带近红外发光材料，试图选择阳离子配位数较大的化合物作为基质，通过调控基质中阴离子基团、配位基团，以及中心阳离子种类，结合利用掺杂离子间能量传递方式等方式来控制材料发光性能，实现宽带发射。基于上述研究思路，已获得了几种适于蓝色光激发，发射近红外光的材料；找到了几种提升材料发光性能的方式，例如，采用Cr3+/Cr4+共存的方式拓宽了材料的发射光谱，弄清了离子共存的原因；利用共掺杂离子间的能量传递不仅可以拓宽材料的发射光谱还可以提升材料的温度稳定性，明确了能量传递机理等；通过阳离子替换同样可以拓宽材料的发射光谱，并提升材料的温度稳定性；通过添加助剂、选取不同的原料等方式，有效地控制了材料的形貌等，有效地提升了材料的实用价值；通过将材料与蓝光LED封装获得了多种发射波段的近红外LED，通过穿透实验、夜视实验等，验证了材料的应用价值。