光子带隙结构调控稀土离子量子剪裁效应及其能量传递机制的研究

In the so-called quantum-cutting process, a high-energy photon can be divided into two, or more, photons of lower energy, in which the quantum efficiency is up to 200%. Such manipulation of photon quantum size can then very effectively increase the overall efficiency of a device Recently, a new concept to further enhance the solar cell efficiency based on the light conversion mechanism has been proposed. Owing to the difficult to control the energy transfer between/among rare-earth ions and luminescence characteristics by traditional method, the external quantum efficiency of luminescence is very low which against the practical application in silicon-based solar battery. Since it is possible for photonic crystal to modulate the photonic state density of photonic band gap and the interaction between excitation light and materials, it will lead to the control of physical process and photoelectric properties of photoelectric materials, and it also provides an effective way to control the process of energy transfer in quantum cutting photoluminescence. In this study, the inverse opal and composite opal photonic crystals with quantum cutting effect are prepared by sol-gel method，and the periodic structure is designed in nano-scale. To further investigate the mechanisms of quantum cutting photoluminescence and energy transfer, the rare earth ions optical behaviors of absorption state, excitation state and spontaneous emission are modulated under photonic crystal bandgap which lead to improve the efficiency of quantum cutting photoluminescence. These studies will be helpful to learn the relationship between material structural and quantum cutting photoluminescence efficiency. It is of important theoretical and practical significance for improving the excited efficiency of rare earth ions, exploring new phosphors materials and optical devices, and this project can possibly be realized by using a rare earth doped quantum cutting phosphor as a down conversion convertor in front of silicon-based solar cell panels.

量子剪裁可以实现高能光子向多个低能光子的转化，其量子效率可接近200%。由于传统研究方法难以对其中的能量传递和发光行为进行有效调控，因此量子剪裁的实际发光效率不高，目前尚未在硅基太阳能电池上得到实用化。光子晶体可调节光子带隙结构中光的态密度变化以及材料与激发光的相互作用程度，实现光电材料中光物理过程和光电性质的调控，为调制量子剪裁发光的电子迁移中间过程提供了一种有效的研究方法。本项目拟通过溶胶-凝胶法制备具有量子剪裁效应的反蛋白石和复合蛋白石结构光子晶体，对其周期结构进行纳米尺度设计，通过光子晶体带隙调控稀土离子的吸收、激发状态以及自发辐射行为提高量子剪裁发光效率，进一步探索量子剪裁发光及其能量传递机制。本项目的实施将有助于认识材料结构与量子剪裁发光效率的关系，对于提高基质材料中稀土离子的受激效率、开发新型荧光粉材料及器件，提高硅基太阳能电池光电转化效率具有重要的理论和现实意义。

本项目针对目前光谱调制材料存在光吸收响应范围窄，能量传递及影响机制不可控，下转换近红外发光外发光效率低等问题，在具有光谱调制效应的光子晶体中，通过光子带隙和Ag纳米微粒等离子体共振局域场协同作用，调控稀土离子在材料中的能量传递过程和受激发射效率，研究光子带隙因素对量子剪裁发光性质的影响及其能量传递机制，并探索光谱调制对太阳能电池光电转换效率的增强作用机制。.一、光子带隙增强下转换发光效率的研究，通过光子晶体的光子带隙效应能够抑制能量传递过程中敏化剂的自发辐射，改变某一能量范围内的光子态密度，从而有利于增加敏化剂与发光中心的能量传递，提高能量传递的效率。因此利用自组装法制备了一系列反蛋白石光子晶体，通过调控光子晶体的带隙位置抑制敏化剂离子的发光，增强稀土离子之间的下转换能量传递效率，提高近红外发光强度。 .二、光子带隙增强合作下转换量子剪裁发光效率的研究，在合作下转换量子剪裁发光中，通过合作下转换的方式进行的能量衰减概率极低。为了解决这一问题，利用光子带隙抑制效应，使能量施主离子的光子态密度分布发生改变，使得处于激发态能级上的电子密度增加，这种阻滞作用有利于合作下转换量子剪裁能量传递过程。