具有协同管理特性的微纳复合结构对太阳电池Shockley-Queisser极限影响的研究

According to the Shockley-Queisser detailed-balance model, the thermodynamics analysis pointed out that the solar cells with high conversion efficiency generally correspond to a high open-circuit voltage, which depends on the solar-cell temperature, the emission solid angle, and the light concentration factor, as well as material properties themselves. To maximize the conversion efficiency, it is key to tailor the above three physical quantities through synergetic management, whereas it is difficult because the sophisticated control over the interaction with electromagnetic waves from ultraviolet to mid-infrared (MIR) regime at the nanometer and micrometer length scales remains highly challenging. Inspired by Saharan silver ants, this project proposes a micro-nanocomposite structure, consisting of a micro-nano-surface and a highly dispersive layer as a gap. The structure is able to cool the temperature through the wavelength selectivity and the MIR radiation; it can also restrict the emission solid angle due to the non-reciprocity and the total internal reflection; the light concentration factor can be improved, too, resulting from the geometrical and wave optical effects. Applying the proposed micro-nanocomposite structure in photovoltaics, the conversion efficiency is expected to be improved and the relationship of the three quantities will be discussed through the provided experimental evidences. This project stems from a basic scientific question: what restrict the conversion efficacy of a single-junction solar cell? To solve the question, the micro-nanocomposite structure with a function of synergetic management is proposed, which possibly exerts an influence on novel effects (e.g., photon recycling) and inspires the new findings and understanding of scientific questions about the emerging perovskite/silicon tandem solar cells.

基于Shockley-Queisser模型的热力学分析指出高转换效率太阳电池具有高开路电压，它除了受材料特性影响外，还受电池温度，辐射立体角和陷光因子三个物理参量的影响。为提高效率需对以上参量进行协同调控，目前主要瓶颈在于缺少同时对从紫外到中红外电磁波在微纳尺度中的行为实施调控的方法。本项目通过与撒哈拉银蚁毛发结构的对比分析，提出设计和制备具有微纳表面与高色散间隙层构成的复合结构，通过其波长选择性和被动辐射效应降低电池温度，利用其非倒易的结构特征和全内反效应限制辐射立体角，并基于几何和波动光学效应提升陷光因子，实现对转换效率的提升并为参量间相互关系的讨论提供实验依据。本项目从探索制约单结电池效率提升的基本科学问题出发，提出具有协同管理特性的微纳复合结构，它对于研究新发现的如光子回收效应也可能存在一定作用，同时对于发现和理解如钙钛矿/晶硅叠层电池中的基本科学问题也将提供有益的启示。

基于Shockley-Queisser模型的热力学分析指出高转换效率太阳电池具有高开路电压，它除了受材料特性影响外，还受电池温度、辐射立体角和陷光因子三个物理量的影响。为提高电池效率需对以上参量进行协同调控，目前主要瓶颈在于缺少同时对从紫外到中红外电磁波在微纳尺度的行为实施调控的方法。本研究受撒哈拉银蚁毛发结构的启发，基于其在太阳光波段所具有的全内反效应和在中红外波段的折射率梯度渐变效应，提出了具有波长选择性的三角锥状微纳复合结构设计，以实现对电池温度、辐射立体角和陷光因子三个物理量的全面调控。通过本项目研究主要取得以下成果：（1）采用干法结合湿法在单晶硅表面成功制备了具有纳米褶皱（特征尺寸约为200纳米）的金字塔（特征尺寸约为2.7微米）微纳复合结构，利用纳米压印技术将微结构转印至聚二甲基硅氧烷形成仿生柔性光子结构，其在0.3-1.2微米的太阳光波段具有96.72%的平均透过率和96.17%的光学雾度，在8-13微米的大气窗口波段具有0.98的热发射率，将其用于晶硅和钙钛矿电池，可提升光电转换效率相对百分比约为3-7%，主要可归结为电池温度和陷光效应方面的改善；（2）对比研究仿生柔性光子结构与撒哈拉银蚁毛发光学和热学特性，结果显示仿生柔性光子结构具有增强的光学反射和辐射散热作用，可将封闭微小空间内空气温度降低0.7-5.6摄氏度；（3）构建了银网栅ITO复合透明电极，进一步改善对电池辐射立体角的调控，所制备的具有PET/Ag-mesh/ITO/P3CT-N/(Cs0.05FA0.54MA0.41)Pb(I0.98Br0.02)3/PC61BM/C60/BCP/Ag结构的柔性钙钛矿电池稳态光电转换效率达到17.50%，4毫米弯折半径下2000次弯折，仍可维持在初始效率的90.19%。基于上述研究，本项目共计发表SCI论文17篇，部分论文已被各类综述及研究论文引用百余次，同时申请发明专利8项，已授权4项。