【作者】 牛士超；

【导师】 韩志武；

【作者基本信息】 吉林大学 ， 仿生科学与工程， 2014， 博士

【摘要】 在太阳能电池领域中，光学损失是影响其效率提高的最重要障碍之一。目前，用于减少太阳能电池表面光学损失的主要途径有两条：一是利用减反射薄膜，二是利用陷光结构。同时，作为地球上阳光辐射中必不可少的部分，紫外光（200-400nm）对于地球上的生命来说至关重要，是必要的，但是，过多的紫外辐射却对人体会造成致命的伤害。因此，对于紫外波段陷光表面的研究同样具有重要的意义，尤其是对于空间装备以及空间探索领域。陷光结构是通过制作一些表面结构来降低表面的反射率，它通过反射、折射和散射作用，将入射光分散到各个角度，从而增加光在太阳能电池等装置中的光程，使光被吸收的效率显著增加。目前，已经研制出的陷光表面有很多种，例如，蜂窝状表面、正弦光栅织构化表面、酒窝状有序表面、周期性金字塔及倒金字塔结构表面、二元光栅表面等，这些陷光表面在众多领域的光学装置上均得到了很好的应用。然而，这些光学结构的实际陷光性能或者陷光效率并没有达到理想的状态。因此，寻求最优化的高效陷光功能表面成为光伏领域研究的热点和难点。受仿生学的启发，本文选取生活在高海拔或高纬度地区等低温、强紫外环境下的蝴蝶作为生物样本，它们分别是翠叶凤蝶、翡翠凤蝶及三种绢蝶。通过紫外可见分光光度计对典型蝴蝶鳞片进行反射光谱测量，发现了翠叶凤蝶和翡翠凤蝶翅膀鳞片在可见光波段均具有优异的陷光特性，五种绢蝶均具有优异的紫外陷光特性。采用体视显微镜、扫描电子显微镜及透射电子显微镜等对典型蝴蝶鳞片陷光结构进行分析，获得了典型蝴蝶鳞片陷光结构参数，建立了仿生陷光结构光学模型，揭示了典型蝴蝶鳞片优异陷光特性机理。对于翠叶凤蝶，其翅膀表面具有两层结构完全不同的鳞片，A型塔状结构对入射光具有相消干涉作用，B型多孔光栅结构对入射光具有衍射作用，两者共同作用实现优异的陷光特性。翡翠凤蝶多层介质膜一维光子晶体同样实现了优异的陷光特性。绢蝶通过在一维光子晶体层中剪切并生成了光栅结构，同时利用光栅光束定向特性以及光子晶体光波选择特性达到优异紫外陷光特性。此外，由于蝴蝶翅膀三维超微结构与角质层复杂折射系数的完美组合超出了目前现有微纳制造技术能力的范围，对于其分级结构整体的复制并不完整，对微纳陷光表面的制造面临挑战，本文直接利用蝴蝶翅膀为生物模板，分别采用溶胶-凝胶以及生物模板法对典型蝴蝶陷光功能表面进行结构和功能的仿生设计与制造。获得了一种对蝴蝶鳞片结构可调的仿生陷光复合材料样品，在溶胀的过程中光谱的反射率逐渐增加，陷光特性减弱，实现了对其陷光性能的调节和控制。通过对比模板与制造样品表面微结构的形状、分布和尺寸参数，证明了仿生制造样本继承了生物样本陷光表面的倒置结构，为进一步地精确研究蝴蝶翅膀表面结构和光学相互耦合效应提供必要的样品支持，进而可以设计出高性能的光学器件。全文共分七章。第一章为绪论，详细阐述了目前陷光结构研究的重大需求，生物功能特性与其表面结构之间的紧密关系以及目前仿生研究的最新进展，介绍了目前对于仿生功能表面微纳制造的最新进展以及面临的重大挑战。第二章是对蝴蝶鳞片陷光功能表面及其光学性能测试，筛选出具有优异陷光特性的蝴蝶物种并对其光学性能进行详细的研究，获得蝴蝶鳞片三维结构参数。第三章是蝴蝶鳞片陷光功能特性的计算与模拟，利用前面对典型蝴蝶翅膀鳞片陷光表面微结构分析得到的试验数据，建立了陷光结构的光学模型，从生物独特功能特性与其表面结构的关系角度出发，利用光子晶体及衍射光栅理论对这些光学模型进行计算与模拟，通过分析陷光结构的光学模型，再现蝴蝶翅膀超微结构与光波的相互作用规律，获得了这些光学模型的模拟结果，通过模拟与计算结果的对比分析确定其优异陷光特性及其形成机理。第四章是陷光功能表面溶胶-凝胶法制造，利用溶胶-凝胶工艺制造了陷光功能表面复合材料样品，通过施加外部刺激实现对陷光表面结构及功能的可调。第五章是仿生陷光功能表面生物模板法制造，以正硅酸乙酯为前驱体，以具有陷光功能特性的蝴蝶翅膀为模板，通过溶胶-凝胶以及选择性腐蚀工艺对蝴蝶翅膀陷光功能表面进行仿生设计及制造，最终获得了陷光表面结构的倒置结构制造样品。第六章是仿生陷光功能表面制造样品性能研究，对溶胶-凝胶及生物模板法制造获取的样品，进行微结构及光学性能的详细对比分析，通过对生物样本及制造样本之间的多角度多手段的对比分析，确定了仿生制造样本对生物样本结构和功能的高精度继承。第八章为结论。本文对于仿生陷光功能表面的研究，将为新型高效陷光结构的研究提供新的思路，如果将这种仿生陷光功能表面应用于光能利用的陷光设计，有望降低光能利用过程中的光学损失，在提高太阳能电池中的光能利用效率方面具有重要的工程应用价值。更多还原

【Abstract】 The optical loss is one of the major obstacles to improve its efficiency of solar cells. Toreduce its surface reflection, there are mainly two ways: one is the use of anti-reflection film; thesecond is the use of light trapping structures. At the same time, as a necessary part of the solarradiation on earth, the ultraviolet (UV,200-400nm) is essential and necessary for life on earth.But exposing in too much UV radiation, then the body will be suffered fatal injuries. Theadvantages and disadvantages of the UV radiation strongly inspired the research interest ofmany research teams to explore and develop the light trapping functional surfaces of spaceequipment. By using reflection, refraction and scattering, light trapping structures scattered theincident light to various angles and thereby increasing the light path in the solar cell, resulting inthe light absorption efficiency is increased significantly. To date, various antireflective structures,such as “honeycomb” surface, sinusoidal grating texture, self-ordered dimple patterns, periodicpyramids, and binary gratings have been extensively studied and developed to enhanceexcellent antireflective efficiency of optical devices. Yet, these optical structures have notachieved an ideal light trapping effect. So, looking forward the ideal light tapping functionalsurface is the hot and difficult areas of photovoltaic research.Inspired from nature, butterfly wings were chosen as a natural model and its features forlight trapping effect were revealed. These butterflies live in a high altitude and high latituderegions, which is a low-temperature of strong ultraviolet environment. It was found that the lighttapping effect is closely related to the ultrahierarchical structures of wing scales. In this paper,three kinds of butterflies with obvious structural color were chosen as natural model. Alcoholdiscoloration experiment determines its structural color characteristics. Using a spectrophoto-meter, the butterfly species with excellent light trapping properties were screened out. Itsmicro-scale structure and light trapping properties were then studied. The optimized3Dconfiguration of the coupling structure was determined using SEM and TEM data. The lighttrapping mechanism of butterfly scales was studied. An optical model was created to check theproperties of this light trapping structure. The simulated reflectance spectra are in concordancewith the experimental ones. Also, the perfect combination of three-dimensional ultrastructure ofbutterfly wings and the complex refractive index of corneum is beyond the capability of currentmanufacturing technology. Although the physical mechanism of light trapping property ofbutterfly wings is well understood, it remains a challenge to create artificial replicas of thesenatural functional structures. Here, a SiO2inverse replica of a light trapping structure in butterflywing scales was synthesized using a method combining a sol-gel process and subsequent selective etching. Using this simple process, the original structures of bio-templates were wellinherited by the structures of the inverse replica. The entire hierarchical structure of butterflywings was successfully retained. These works provide the necessary support for further study ofthe coupling effects between precise structure and the optical effect. In turn, it is possible todesign the high-performance optical components.This paper is divided into seven chapters. The first chapter is an introduction. The majorneeds of the light trapping structures were introduced. Close relations between biologicalfeatures and the surface structures and the latest progress of bionic were also introduced. Allthese introductions fully demonstrated the importance and necessity of the works in this article.The second chapter is the light trapping surface of butterfly and its optical test. The detailedthree-dimensional structure parameters were obtained. Chapter three was the mechanism of theoptical functional surface of butterfly scales. First, the optical model of the light trappingstructure was established using experimental data obtained previously. From the perspective ofthe relationship between the surface structures of the unique features of biology, the opticalmodel was analyzed. Using photonic crystals and diffraction grating theory, the light trappingmechanism of butterfly scales was studied. Chapter four is manufacturing the light trappingfunctional surface by using sol-gel method. A composite sample obtained using sol-gel process.The light trapping surface structure was achieved tunable by external stimulus. Chapter five isthe fabrication of the bionic light trapping surface using the butterfly wings as the bio-template.The intricate light trapping structure was replicated in three steps by a synthetic methodcombining a sol-gel process and subsequent selective etching. The detailed and carefulparametric comparison of the morphology, dimensions and distributions of the extremelysimilar textured micro-structures between the original template and the inverse replica isachieved. Afterwards, it is conformed that the original structures of bio-templates are wellinherited by the structures of the inverse replica. Chapter six is the light trapping study ofreplicated samples. The parametric comparisons of the morphologies and structures between theoriginal template and the replica were carefully conducted, and it was found that the originalstructures of bio-templates were well inherited by the structures of the inverse replica. Chapterseven is the conclusions.Studies of the bionic light tapping surface in this paper will provide a new way ofdesigning new efficient light trapping structures. If this bionic light tapping surfaces could beused in the optical trapping design of solar cells, it is expected to reduce the optical loss, whichhas important application value in improving the light use efficiency of solar cell.更多还原