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

提出的研究涉及到发光材料的制造和表征，这些发光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，它们不能利用能量小于其能带隙的光子，而能量大于能带隙的光子只使用其部分能量来产生电流：其余的转化为热量。解决这个问题的办法是使太阳光谱适应太阳能电池。这可以通过将两个亚带隙能量的光子转换为一个高于带隙能量的光子来实现（上转换），或者通过将一个能量远高于带隙的光子转换为两个（或更多）仍然高于带隙的光子来实现（下转换）。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限制之上。该项目研究了使用镧系掺杂材料实现太阳能电池上转换和下转换的潜力。虽然镧系离子在高效光谱转换方面具有许多优点，但它们往往在较窄的光谱范围内吸收光子，并且它们的绝对吸收强度相对较弱。为了提高转换太阳光谱的影响，应特别注重用吸收剂提高上转换和下转换过程的灵敏度，这种吸收剂可以有效地吸收宽光谱范围内的太阳辐射，并将这种能量转移到光谱转换的镧系离子上。高素质的人员将在敏化镧掺杂体和纳米结构材料的制造方面进行培训，以及使用时间分辨发光技术进行研究。将太阳能光谱转换的最佳材料纳入太阳能电池，其中将进行原理验证实验，以证明太阳能电池效率的提高。光伏装置效率的显著提高将为更有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.