Composite Luminescent Materials and Light-Harvesting Systems

答:光伏发电。光伏能源系统的进步需要比现在的硅电池更好地利用太阳光谱。硅太阳能电池板本质上优化了红光和近红外波长的有效收集，但由于被称为热化的能量损失机制，在可见光谱的其他部分效率较低。此外，长波红外辐射根本没有被收集。我们使用基于荧光的太阳能电池系统来更好地收集可见光。基于荧光的太阳能电池使用荧光粉或量子点来吸收光，然后在选定的波长重新辐射光。在吸收和再辐射过程中，光的方向是随机的，它可以在收集板中被波导引导，并被引导到收集板的边缘，在那里小型、高效的太阳能电池可以实现高转换效率。为了尽量减少光在集热器板中的再吸收，可以优化荧光粉或量子点的分布和密度或在空间上进行图像化。我们正在研究使用空间图案荧光粉，使集中的阳光到达荧光粉，同时保持一个有效的波导系统，使荧光到达集热器板的边缘。为了获取长波红外辐射，我们正在研制GaSb（锑化镓）薄膜太阳能电池。GaSb吸收能量低至0.7电子伏（eV）的光子，从而可以有效地收集0.7-1.1电子伏的光子。我们正在从大块靶材溅射GaSb，允许化学计量（成分）变化，从而实现薄膜半导体性能的优化。发光。粉末材料中的电致发光是产生柔性光片的一种有吸引力的方法。在这里，粉末可以夹在两个电极之间（其中一个是透明的），在施加交流电压时，可以观察到粉末的发光。传统的电致发光粉末是由硫化物制成的，但我们正在开发氧化粉末，如硅酸锌粉。这些材料的活化需要加入第二导电相。虽然发光二极管已经在快速增长的固态照明市场上证明了自己可以取代白炽灯和荧光灯，但它们本质上是点源，因此不适合需要薄而柔性的光源的应用。这项工作的目标是提高用于照明、标牌和显示器的柔性光片的亮度和稳定性。电致发光的一种特殊用途是在黑暗环境中用于标记紧急出口或家具或设备边缘的发光胶带。未来更大的市场是可折叠电视。

A. Photovoltaics. Advances in photovoltaic energy systems require better use of the solar spectrum than today's silicon cells achieve. Silicon solar panels are inherently optimized for efficient harvesting of red and near-infrared wavelengths but are less efficient over other parts of the visible spectrum due to an energy loss mechanism called thermalization. In addition, longer wave infrared radiation is not harvested at all. Our approach to better harvest visible light uses fluorescence-based solar cell systems. Fluorescence based solar cells use phosphors or quantum dots to absorb light and then re-radiate the light at selected wavelengths. During the absorption and re-radiation process, the light is randomized in direction and it can be wave-guided in a collection plate and directed to the edges of the plate where small, high efficiency solar cells can achieve high conversion efficiency. To minimize re-absorption of light in the collector plate the distribution and density of phosphors or quantum dots may be optimized or spatially patterned. We are investigating the use of spatially patterned phosphors to allow concentrated sunlight to reach phosphors while maintaining an efficient waveguiding system to allow the fluorescence to reach the edges of the collector plate. For the harvesting of long wave infrared radiation we are developing GaSb (gallium antimonide) thin film solar cells. GaSb absorbs photons having energies from as low as 0.7 electron volts (eV) which allows the efficient harvesting of 0.7-1.1 eV photons. We are sputtering GaSb from bulk targets that allow the stoichiometry (composition) to be varied thereby enabling the optimization of thin film semiconductor properties. B. Luminescence. Electroluminescence in powder materials is an attractive approach to producing flexible sheets of light. Here a powder may be sandwiched between two electrodes (one of which is transparent) and upon the application of an AC voltage, luminescence is observed from the powder. Traditional electroluminescent powders are made from sulphides, however we are developing oxide powders such as zinc silicate powder. Activation of these materials requires the incorporation of a second conductive phase. Whereas light emitting diodes have proven themselves in the rapidly growing solid state lighting market to replace incandescent and fluorescent lamps, they are inherently point sources and therefore do not lend themselves to applications where thin, flexible sheets of light are needed. The goal of this work is to improve the brightness and stability of flexible light sheets for applications in lighting, signage and displays. One specific use of electroluminescence is for glowing tapes that can mark emergency exits or edges of furniture or equipment in a dark environment. A larger future market is for roll-up televisions.