Spectral Conversion via Sensitized Up- and Down-conversion with Micro- and Nano-crystalline Phosphors

拟议的研究涉及到发光材料的制备和表征，这些材料可以改变太阳光谱，从而有可能提高太阳能电池的效率。太阳能电池的一个基本效率限制是，它们无法利用能量小于其带隙的光子，而能量大于该带隙的光子只使用其部分能量来产生电流：其余的能量被转化为热。这个问题的一个解决方案是使太阳光谱适应太阳能电池。这可以通过将两个子带隙能量的光子转换为高于带隙的能量的光子(上转换)，或者通过将能量远高于带隙的光子转换为仍然高于带隙的两个(或更多)光子(下转换)来实现。后一种解决方案的任何一种方法都具有显著的潜力，可以将太阳能电池的效率提高到理论效率极限以上。该项目研究了使用稀土掺杂材料实现太阳能电池上转换和下转换的可能性。虽然稀土离子具有许多高效的光谱转换优势，但它们往往在较窄的光谱范围内吸收光子，其绝对吸收强度相对较弱。为了提高转换太阳光谱的影响，工作应特别侧重于用在较大光谱范围内有效吸收太阳辐射的吸收体提高上转换和下转换过程的敏感度，并将这种能量转移到光谱转换的稀土离子上。高素质的人员将接受有关敏化稀土掺杂块体和纳米结构材料的制备以及使用时间分辨发光技术进行研究的培训。转换太阳能光谱的最佳材料将被纳入太阳能电池中，其中将进行原理验证实验，以证明太阳能电池效率的提高。光伏设备效率的显著提高将为开发更高效的替代能源铺平道路。

The proposed research involves the fabrication and characterization of luminescent materials which modify the solar spectrum, and thereby have potential to enhance the efficiency of solar cells. A fundamental efficiency limitation of solar cells is that they are not able to utilize photons with energy less than their energy band-gap, and photons with energy greater than this band-gap use only part of their energy to create electric current: the rest is converted into heat. A solution to this problem is to adapt the solar spectrum to the solar cell. This can be achieved by converting two photons of sub-band-gap energy to a photon of energy above the band-gap (up-conversion), or by converting a photon with energy well above the band-gap to two (or more) photons still above the band-gap (down-conversion). Either method for this latter solution has significant potential to enhance solar cell efficiency above theoretical efficiency limits. The project investigates the potential of using lanthanide-doped materials to implement up-conversion and down-conversion for solar cells. While lanthanide ions possess many advantages for efficient spectral conversion, they tend to absorb photons over narrow spectral ranges, and their absolute absorption strength is relatively weak. To improve the impact of converting the solar spectrum, work shall be particularly focused on sensitizing the up-conversion and down-conversion processes with absorbers which efficiently absorb solar radiation over a wide spectral range, and transfer this energy to spectrally-converting lanthanide ions. Highly qualified personnel will be trained in the fabrication of sensitized lanthanide-doped bulk and nano-structured materials, as well as their investigation using time-resolved luminescence techniques. Optimal materials for conversion of the solar spectrum will be incorporated into solar cells, wherein proof-of-principle experiments will be conducted to demonstrate enhancement of solar cell efficiency. Significant enhancement of photovoltaic device efficiency will pave the way to a more efficient alternative energy source.