基于能量传递的宽谱调制近红外下转换纳米发光薄膜研究

Nanocrystalline luminescent films with broadband down-conversion used for improving the efficiency of silicon solar cell will be prepared by sol-gel and pulsed laser deposition (PLD) technique. Near-infrared emission phosphors based on alkaline earth complex oxides are designed in the light of the energy transfer, in which ions Ce3+, Eu2+, Bi3+, Pb2+, vanadates, molybdates and tungstates with intense broad band absorption and emission are selected as sensitizers, and Yb3+, Pr3+ or RE3+-Yb3+ (RE = Tm, Pr, Er, Tb, Nd, Ho) are used as acceptors. The mechanisms of energy transfer and the possibilities of efficient near-infrared emission are analyzed. In order to improve the energy transfer efficiency, alkaline earth ions or O2- are substituted partially or completely by other two- / single-valence cations or halogen anion ions to tune the absorption and emission wavelength of donors. Thus the energy transfer process are changed and the solar spectra ranging from near ultraviolet to blue-green region could be efficiently converted to near-infrared emission by the quantum cutting, which adapts the solar spectrum to better match the solar cell and improves the silicon solar cell efficiency. Moreover, the stabilities of the luminescent films are also investigated in detail in order to match well with the lifetime and the application environment of the silicon solar cell. In order to obtain the excellent near-infrared emission nanocrystalline luminescent films with broadband down-conversion based on energy transfer, the parameters of the prepare process of sol-gel and PLD technologies are optimized.

采用溶胶-凝胶（Sol-gel)和脉冲激光沉积(PLD)技术制备用于提高硅基太阳能电池光电转换效率的宽带光谱调制近红外下转换纳米发光薄膜。以能量传递为基础，选择具有宽带吸收和发射特性的Ce3+、Eu2+、Bi3+、Pb2+及钒酸根、钼钨酸根等离子或基团为敏化剂，Yb3+、Pr3+或离子对RE3+-Yb3+ (RE = Tm, Pr, Er, Tb, Nd, Ho)为激活剂，研究碱土复合氧化物为基质的能量传递和近红外发光机制。通过阳离子及卤素阴离子部分或完全取代基质中碱土离子或O2-来调节基质组成，进而调控敏化剂的配位场及其吸收与发射波长,改变能量传递过程,提高能量传递效率，实现将太阳光谱中的近紫外-蓝绿光高效转换成硅太阳能电池可利用的近红外光。调控成膜过程,深入研究成膜机理及薄膜稳定性和透光性，获得用于提高硅基太阳能电池效率的稳定、透明、高效的宽带光谱调制近红外下转换纳米发光薄膜。

面对化石能源逐渐走向枯竭和环境污染的日益严重，太阳能作为绿色新能源重要组成部分和最有发展前景的新能源受到广泛重视太阳能电池成为研究热点，而技术最为成熟和应用最为广泛的硅基太阳能电池市场占有率超过90％，但其15%左右的实际光电转换率大大低于理论最大值30%，其主要原因是硅基太阳能电池的响应曲线与太阳光谱的严重不匹配。基本此，项目采用光谱调制的方法通过纳米光转换薄膜将硅基太阳能电池无法吸收的太阳光转化成可以吸收的光，以提高硅基太阳能电池的光电转换效率。.项目主要研究了下转换和上转换两类纳米光转换薄膜层，下转换光转换层是将能量高于硅带隙（Eg =1.12eV, λ=1100 nm)的太阳光子转化成一个或两个电池可以吸收的长波可见光或近红外光子（λ<1100 nm）,上转换层是将电池无法吸收的两个或多个低能太阳光子转换成一个可见光或近红外光子，从而提高对太阳光的吸收率并，达到提高电池效率和减少热量产生目的。项目以能量传递为基础，选择具有宽带吸收特性的Ce3+、Eu2+、Bi3+， Mn4+及钒酸根离子或基团为敏化剂，含有Ln3+的钒酸盐、硼酸盐、钼酸盐等为基质，Yb3+，Pr3+，Nd3+或RE3+-Yb3+ (RE = Tm, Pr, Er, Tb, Nd, Ho)为激活剂来设计下转换材料，增加了Yb3+掺杂浓度，拓宽了吸收截面，提高了能量传递效率和近红外下转换发光强度；采用Sol-gel, 水热、共沉淀法合成了Yb3+-RE3+共掺的氟化物和简单、复合氧化物上转换发光材料。这些上/下转换材料可将高能或低能太阳光子转换成硅基电池可以吸收的长波可见光或近红外光。筛选出了钼酸盐、钒酸盐和纳米氟化物发光材料并采用sol-gel、有机胶与荧光粉混合的方法制备了薄膜，研究了薄膜厚度、致密性、剥离过程、粉体颗粒大小等对膜发光强度、透明性等的影响；结果表明纳米粉体得到的薄膜透明性较好；而胶粉混合的方法简单易用，为其在提高硅基电池效率方面的应用打下了良好基础。