Phosphor Nanostructures: Synthesis and Applications

目的：该提案的首要目标是研究和开发钇铝石榴石（YAG）基氧化物磷光体纳米粉末作为荧光材料，其比有机或量子点替代品稳定得多。目标包括获得荧光磷光体纳米颗粒的基本理解，并长期关注主要应用领域，包括荧光太阳能聚光器和microLED。重要性：荧光太阳能聚光器（FSC）可以使未来的光伏（PV）建筑窗户用于建筑集成光伏（BIPV）行业。在这里，一个建筑物的窗户收集阳光，并将其引导到窗户的边缘，在那里它被硅太阳能电池转化为电能。纳米尺寸方面允许可见光散射最小化。BIPV组件标准规定了25年的使用寿命。这可以通过非常稳定的氧化物荧光材料来满足，最公知的材料是含有稀土或过渡金属活化剂的通用YAG基质。有机染料和量子点无法满足这些寿命要求。MicroLED提供了一种新的显示革命的前景，其中开发良好的无机固态p-n结光发射器被显著地按比例缩小，以产生对于手机显示器足够小的红/绿色/蓝色（RGB）显示像素。单个颜色子像素所需的尺寸是？10µm，可在视网膜屏幕手机显示屏中实现60µm RGB像素。microLED的优点包括宽色域，折叠/卷起显示器的机械灵活性以及与当前LCD和OLED屏幕相比降低6倍的功耗。这些微发光二极管需要优化的发射白色光的纳米磷光体。方法：我们将专注于荧光纳米粒子的基本但与工业相关的方面。发射中心之间的能量转移的研究将通过光谱学进行，其中在仅核和核壳的YAG纳米荧光粉中控制敏化原子（Ce）和激活剂（Mn、Nb）的浓度和相关发射强度。我们的目标是扩展我们最近研究的表面氧化技术，以创建Mn 2+或Mn 4+电荷补偿活化剂。 钇、铝和铈都占据YAG基质中的3+价态。当Mn占据Al位点时，可能存在局部电荷不平衡。电荷不平衡提供了一个非辐射路径作为一个发光猝灭的网站，应避免松弛。YAG基质非常适合作为具有稀土掺杂剂Nd的红外发射器，其中它用于吸收800 nm范围内的近红外辐射，在1100 nm处具有荧光。为了吸收可见光，将利用Ce和Nd之间的能量转移。

Objectives: The over-arching objective of this proposal is the study and development of yttrium aluminum garnet (YAG)--based oxide phosphor nanopowders as fluorescent materials that are much more stable than either organic or quantum dot alternatives. Goals include gaining a fundamental understanding of fluorescent phosphor nanoparticles with a long term view to primary application areas including fluorescent solar concentrators and microLEDs. Significance: A Fluorescent Solar Concentrator (FSC) can enable future photovoltaic (PV) building windows for the Building Integrated PhotoVoltaic (BIPV) industry. Here a building window collects sunlight and waveguides it to the edges of the window where it is converted into electricity by silicon solar cells. The nanosize aspect allows visible light scattering to be minimized. A 25 year lifespan is dictated by BIPV component standards. This may be satisfied by very stable oxide fluorescent materials, the best known materials being versatile YAG hosts containing rare earth or transition metal activators. Organic dyes and quantum dots are unable to meet these lifespan requirements. The MicroLED offers the promise of a new display revolution in which well--developed inorganic solid state p-n junction light emitters are dramatically scaled down to produce red/green/blue (RGB) display pixels small enough for cellphone displays. The required size of a single colour sub-pixel is ?10µm to enable 60µm RGB pixels in a retina screen cellphone display. Benefits of the microLED include wide colour gamut, mechanical flexibility for fold-up/roll-up displays and a 6--fold power consumption decrease compared to current LCD and OLED screens. Optimized white--emitting nano-phosphors are required for these microLEDs. Approach: We will focus on fundamental but industrially relevant aspects of fluorescent nanoparticles. Investigation of energy transfer between emission centers will be carried out via optical spectroscopy, in which the concentrations and associated emission intensities of the sensitizing atom (Ce) and activators (Mn, Nb) are controlled in both core--only and core--shell YAG nanophosphors. We aim to extend the surface oxidation technique we have recently investigated to create Mn2+-or Mn4+ charge--compensated activators.   Yttrium, aluminum, and cerium all occupy 3+ valence states in the YAG host. When Mn occupies an Al site, there may be a local charge imbalance. The charge imbalance provides a non--radiative pathway for relaxation acting as a luminescence quenching site which should be avoided. The YAG host is well suited as an infrared emitter with rare earth dopant Nd where it is used to absorb near-infrared radiation in the 800nm range with fluorescence at 1100nm. In order to absorb visible light, energy transfer between Ce and Nd will be utilized.