Phosphor Nanostructures: Synthesis and Applications

目的：这项计划的总体目标是研究和开发基于Y铝石榴石(YAG)的氧化物荧光粉纳米粉末作为荧光材料，它比有机或量子点替代品更稳定。目标包括对荧光荧光粉纳米颗粒有一个基本的了解，并着眼于主要应用领域，包括荧光太阳能聚光器和微发光二极管。意义：荧光太阳能集中器(FSC)可以为建筑集成光伏(BIPV)行业的未来光伏(PV)建筑窗户提供支持。在这里，一扇建筑窗户收集阳光，并将其传导到窗户的边缘，在那里硅太阳能电池将阳光转化为电能。纳米尺寸的方面允许可见光散射最小化。25年的寿命由BIPV组件标准决定。这可以通过非常稳定的氧化物荧光材料来满足，最著名的材料是含有稀土或过渡金属激活剂的多用途的YAG基质。有机染料和量子点无法满足这些寿命要求。微LED有望带来一场新的显示革命，在这场革命中，成熟的无机固态p-n结光发射器将大幅缩小规模，以生产出足以用于手机显示器的红/绿/蓝(RGB)显示像素。单色亚像素的大小要求为？10微米，才能在视网膜屏幕手机显示屏上启用60微米RGB像素。与当前的LCD和OLED屏幕相比，MicroLED的优点包括宽色域、折叠/卷起显示器的机械灵活性以及功耗降低6倍。优化的白光--这些微LED需要发射纳米荧光粉。方法：我们将把重点放在荧光纳米颗粒的基本但与工业相关的方面。研究发射中心之间的能量转移将通过光学光谱进行，其中敏化原子(Ce)和激活剂(Mn，Nb)的浓度和相关发射强度在只有核的和核壳的两种情况下都是可控的。我们的目标是扩展我们最近研究的表面氧化技术，以产生Mn2+或Mn4+电荷补偿的激活剂。Y，Al和Ce都占据了YAG基质中的3+价态。当Mn占据Al位时，可能存在局部电荷不平衡。电荷不平衡为弛豫提供了一条非辐射路径，起到了发光猝灭的作用，应该避免这种情况。用稀土掺杂的Nd作为红外发射体，可以吸收800 nm波段的近红外辐射，荧光波长为1100 nm。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.