100nm周期蛾眼结构制备及其表面拉曼增强性能

以多孔氧化铝(AAO)为模板,基于聚氨酯丙烯酸酯(PUA)在紫外曝光前后的表面能变化的特性,利用逆紫外固化纳米压印技术实现纳米蛾眼结构复制成型。分析图形复制过程中界面间的粘附功差异,根据红外光谱对C=C双键的转化速度来表征PUA的固化程度进而优化制作工艺,在柔性聚对苯二甲酸乙二酯薄膜表面制备出周期为100 nm的PUA大面积高深宽比柱状纳米结构阵列。利用具有蛾眼纳米结构的银金属薄膜,进行表面拉曼增强特性实验,得到了葡萄糖分子的表面增强拉曼散射效应。     

中红外波段仿蛾眼表面高斯面形抗反射微纳结构优化

基于严格耦合波分析理论,设计中波红外波段3~5μm的仿生蛾眼表面高斯面形周期阵列抗反射微纳结构,用三维有限时域差分法进行仿真模拟优化,分析了结构阵列周期、占空比、刻蚀深度对反射率和透过率的影响,比较高斯面形、抛物面形、圆锥形结构模型抗反射效果,给出了最优化参数组合。分析了加工过程中周期、占空比和刻蚀深度以及外部形状轮廓偏差对蛾眼微纳结构的影响,给出了在要求抗反射效果下允许的结构参数公差尺寸范围和建议加工尺寸,结果得到的抗反射结构反射率低于3%~5%,透过率高于90%。     

微结构对聚合物漫反射性能的影响

利用挤塑滚压成型工艺把滚轮上的微结构转印至聚合物薄板表面上。通过光学显微镜观察到微结构在聚合物表面分布均匀。利用三维轮廓仪ZIP250测量聚合物表面微结构尺寸,三角形排布与六边形排布微结构的复制率分别可以达到98.1%、99.8%,表明微结构填充完整,复制效果良好。与金属反光材料相比,漫反射测试结果表明金属反光材料的漫反射率不足10%,表面带有三角形排布、六边形排布微结构的聚合物薄板,漫反射率最高分别可以达到98%、100%。     

紫外固化浇铸法制作PUA蛾眼结构

本文采用聚氨酯丙烯酸酯(PUA)通过紫外固化浇铸复制多孔氧化铝(AAO)模板制作蛾眼微结构。PUA低粘度和低表面能特性保证了高深宽比柱状阵列结构的精确复制。测量制备的蛾眼结构与水的接触角大于150°,得出蛾眼结构具有超疏水的表面特性,分析了超疏水机理;测量分析了蛾眼结构在400nm-800nm波段的表面透射率较表面无图形的聚对苯二甲酸乙二醇酯(PET)薄膜有显著提高,且周期越小的蛾眼结构提高越明显。     

多层增透膜对铒硼硅酸盐玻璃光学性质的影响

玻璃表面由于反射作用会使光能损失.为了减少玻璃表面的反射损失,可以通过在表面镀增透膜来解决.研究了多层增透膜对铒硼硅酸盐玻璃可见光透过率的影响.在理论上比较了不同膜系结构(层数不同)的增透膜对铒硼硅酸盐玻璃的增透效果.采用了六层膜的设计,并对镀膜前后玻璃的反射率和透过率进行了测试,玻璃在可见光区的430nm波段到800m波段的平均反射率从原来的7.5%左右下降到了1%左右,其吸收光谱曲线的最高透过率从未镀膜前的80%左右提高到了97%左右.同时,镀膜后的铒硼硅酸盐玻璃在0.53μm处的透过率仍然保持在0.01%(光密度D0.53=4),而可见光透过率达到了65%,比镀膜前提高了10%左右,玻璃的可视性得到了明显的改善.     

等离子体增强原子层沉积Al_2O_3钝化多晶黑硅的研究

黑硅的纳米结构可以大大降低硅表面的入射光反射率,同时由于比表面积的增加使其钝化成为难题,从而影响其太阳电池的性能。等离子体增强原子层沉积(PEALD)法沉积的Al2O3钝化层具有良好的保型性和致密性,适用于黑硅纳米微结构的钝化。本文使用金属辅助化学法制备多晶黑硅,再经低浓度碱溶液处理优化黑硅结构,最后用PEALD沉积了不同厚度的Al2O3钝化层。采用扫描电镜、分光光度计和少子寿命测试仪对黑硅的表面形貌、减反射特性和少子寿命变化进行了分析。结果表明碱溶液处理后黑硅表面结构变得更为平滑,Al2O3钝化的黑硅经退火后少子寿命达到8.96μs,在可见光范围内反射率降低至3.7%,与传统制绒工艺的多晶硅片相比性能有明显提升。     

湿法腐蚀硅片并生长氧化锌纳米棒作为太阳能电池减反层研究

在硅基太阳能电池表面制备减反层可以有效降低硅表面的反射率, 提高吸收率, 从而提高硅基太阳能电池的光电转换效率。本研究利用四甲基氢氧化铵(Tetramethyl Ammonium Hydroxide TMAH)溶液对(100)单晶硅进行各向异性腐蚀, 在表面腐蚀出金字塔结构, 得到了最低为6%左右的反射率。然后采用水热法在该衬底生长氧化锌纳米棒, 得到了最低小于3%的反射率, 比单采用腐蚀或者ZnO纳米棒生长的硅表面的反射率更低。这种减反方法工艺简单、高效, 有望得到应用。     

利用金属辅助化学腐蚀法在硅表面获得纳米绒面结构以提升多晶硅太阳电池效率

在硅片表面制备绒面结构能够有效降低太阳光在硅片表面的反射损失,是提高太阳能电池转换效率的一条重要途径。通过真空热蒸发法在多晶硅片上沉积纳米银颗粒,利用金属辅助化学腐蚀(MACE)法,制备了不同腐蚀时间下的纳米绒面结构,其中,腐蚀时间为60s的纳米绒面的平均反射率低至4.66%(300~1100nm)。同时,对腐蚀时间为60s的纳米绒面用KOH溶液进行优化处理,将KOH处理前后的多晶硅片采用常规电池工艺进行电池制备研究。对比发现,经过KOH处理后的电池效率比未经KOH处理的电池效率提高了0.43%。     

光学显示PC镜片多层反射膜的设计与制备

光学显示仪器前的镜片需要通过镀膜来对特定波段形成高反射,国内绝大多数的光学显示镜片还是玻璃,本文以聚碳酸酯(PC)镜片作为基底,采用真空镀膜技术,在聚碳酸酯(PC)镜片上镀高反射膜,研究了不同膜系结构(层数不同)的反射膜对特定波段的反射效果。研究结果表明,采用了5层膜的设计,PC在可见光区的400nm波段到700nm波段的最高反射率从9.5%上升到85%。PC在特定波段的反射率得到了明显的提高。     

金刚线切割多晶硅片表面减反射绒面的制备

为解决金刚线切割多晶硅片表面制绒的问题,提出了一种创新的两步腐蚀制备硅表面陷光结构的方法。先以浓硫酸作为添加剂去除表面线痕,然后通过酸雾腐蚀法获得一种微米纳米复合的多孔陷光结构。样品在300～1100nm波长范围内的平均光反射率被降至8.6%,减反射效果优良,少子寿命提升0.6μs以上。此方法具有操作简单,无需复杂设备,成本低等优点,易实现工业化生产。     

Guided-mode resonant grating filter with an antireflection structured surface

We describe a new structure of guided-mode resonant grating (GMRG) filters with low sideband reflectance. This GMRG filter consists of a high-index thin film on an antireflective structured surface called "moth-eye structure." Since the high-index film undulates along the surface structure, the film acts as a modulated optical waveguide. An incident light wave satisfying a resonant condition is reflected by the GMRG filter, and nonresonant light waves pass through the filter. This GMRG filter is valid for reducing reflection of nonresonant light waves in a wide spectral range. The resonant reflection of this new filter was investigated by numerical calculation based on an electromagnetic grating analysis. In the case of a triangular antireflective surface structure whose thickness is 2x greater than its period, the sideband reflectance for nonresonant light waves was lower than 0.5% for TM-polarized light in a wide range of wavelengths.     

An efficient visible light photocatalyst prepared from TiO<Subscript>2</Subscript> and polyvinyl chloride

An efficient visible light photocatalyst has been prepared from TiO₂ nanoparticles and a partly conjugated polymer derived from polyvinyl chloride (PVC). It was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), UV–visible diffuse reflectance spectroscopy (UV–Vis DRS), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The visible light photocatalytic activity of the as-prepared photocatalyst was evaluated by the photocatalytic degradation of Rhodamine B (RhB) under visible light irradiation. The XPS, FT-IR, and Raman spectra show that the partly conjugated polymer derived from PVC exists on the surface of the TiO₂ nanoparticles. The UV–Vis DRS, XRD, and TEM results reveal that the modification of the partly conjugated polymer can obviously improve the absorbance of the TiO₂ nanoparticles in the range of visible light and hardly affect their size and crystallinity. The visible light photocatalytic activity of the as-prepared TiO₂ nanocomposites is higher than that of commercial TiO₂ (Degussa P25) and comparable with those of visible light photocatalysts reported in the literature. Their visible light photocatalytic stability is also good. The reasons for their excellent visible light photocatalytic activity and the major factors affecting their photocatalytic activity are discussed.     

Angle dependent optical properties of polymer films with a biomimetic anti-reflecting surface replicated from cylindrical and tapered nanoporous alumina

Anodic porous alumina nanostructures have been fabricated with tapered and cylindrical pores with a spacing of 100 and 200 nm and depth of 180-500 nm. The porous nanostructures were replicated into polymer films to create a moth-eye anti-reflecting surface by a roll-to-roll UV replication process. The angle dependent optical transmission of the resulting polymer films exhibited up to a 2% increase in transmission at a normal angle and up to a 5% increase in transmission at a 70° angle of incidence to an equivalent film with a surface replicated from polished aluminum. No significant difference was observed between the optical performance of moth-eye surfaces formed from cylindrical and tapered nano-pores.     

Synthesis of multifunctional nanostructured zinc-iron mixed oxide photocatalyst by a simple solution-combustion technique

A series of nanostructure zinc-iron mixed oxide photocatalysts have been fabricated by solution-combustion method using urea as the fuel, and nitrate salts of both iron and zinc as the metal source. Different characterization tools, such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance UV-visible spectra (DRUV-vis), electron microscopy, and photoelectrochemical measurement were employed to establish the structural, electronic, and optical properties of the material. Electron microscopy confirmed the nanostructure of the photocatalyst. The synthesized photocatalysts were examined towards photodegradation of 4-chloro-2-nitro phenol (CNP), rhodamine 6G (R6G), and photocatalytic hydrogen production under visible light (λ ≥ 400 nm). The photocatalyst having zinc to iron ratio of 50:50 showed best photocatalytic activity among all the synthesized photocatalysts.     

Hierarchical Metal/Semiconductor Nanostructure for Efficient Water Splitting

A hierarchically patterned metal/semiconductor (gold nanoparticles/ZnO nanowires) nanostructure with maximized photon trapping effects is fabricated via interference lithography (IL) for plasmon enhanced photo‐electrochemical water splitting in the visible region of light. Compared with unpatterned (plain) gold nanoparticles‐coated ZnO NWs (Au NPs/ZnO NWs), the hierarchically patterned Au NPs/ZnO NWs hybrid structures demonstrate higher and wider absorption bands of light leading to increased surface enhanced Raman scattering due to the light trapping effects achieved by the combination of two different nanostructure dimensions; furthermore, pronounced plasmonic enhancement of water splitting is verified in the hierarchically patterned Au NPs/ZnO NWs structures in the visible region. The excellent performance of the hierarchically patterned Au NPs/ZnO NWs indicates that the combination of pre‐determined two different dimensions has great potential for application in solar energy conversion, light emitting diodes, as well as SERS substrates and photoelectrodes for water splitting.     

Nearly zero reflectance of nano-pyramids and dual-antireflection coating structure for monocrystalline silicon solar cells

The effect of two-step surface treatment on monocrystalline silicon solar cells was investigated. We changed the nanostructure on pyramidal surfaces by wet nano-texturing so that less light is reflected. The two-step nano-texturing process reduces the average reflectance to about 4% in the 300-1100 nm wavelength region. The use of an antireflection coating resulted in an effective reflectance of 1%. We found that the reflectance obtained by wet nano-texturing was lower than that obtained by conventional alkaline texturing. Thus, we can expect a further increase in the efficiency of silicon solar cells with two-step nano-texturing by a wet chemical process.     

Plasmon-triggered living photopolymerization for elaboration of hybrid polymer/metal nanoparticles

Surface plasmon resonance can be used to manipulate light at the nanoscale. It was used here to trigger photopolymerization of an atom transfer radical polymerization (ATRP) molecular system, leading to a thin polymer shell at the surface of the metal nanostructure. The polymerization can be reactivated from the first polymer shell to covalently graft a second monomer layer with precise control over the thickness at the nanometric scale, depending on the photonic parameters. This route can be applied to different nanoobjects and allows an anisotropic surface modification in agreement with the spatial localization of the enhanced electromagnetic field near the nanostructure. This new route opens the door towards the preparation of multifunctional hybrid metal/polymer nanostructures.     

Mesoporous Au/TiO2 composites preparation,characterization, and photocatalytic properties

In this work, mesoporous Au/TiO₂ composites have been synthesized and tested on photodegradation of methylene blue dye solution. Mesoporous TiO₂ prepared at 450 °C using triblock polymer F127 as structure-directing agent was applied as substrate, while various HAuCl₄ concentrations were used for Au loading through deposition-precipitation method using urea as precipitator and hydrogen reducing process. The influences of Au loading on the microstructures of mesoporous TiO₂ including degree of dispersion, particle size, surface area, light absorption, and band gap were studied with transmission electron microscopy (TEM), X-ray diffraction (XRD), diffuse reflection infrared Fourier transformed spectroscopy (DRIFT), N₂ adsorption–desorption isotherm analysis (BET), and UV–Vis diffuse reflectance spectra. With Au loading, the size of TiO₂ nanoparticles in Au/TiO₂ composites is similar as that of TiO₂ substrate. However, the degree of dispersion was greatly improved. Furthermore, an obvious surface plasmon resonance centered at 570 nm was found in UV–Vis diffuse reflectance spectra for Au/TiO₂ composites. Au loading also induced an obvious red shift of light absorption from UV region to visible region and strengthened both UV and visible light absorption in contrast to substrate. Photodegradation results verified that photocatalytic activity of mesoporous TiO₂ was improved by Au loading. 0.25%Au/TiO₂ composite showed the highest activity, which may be ascribed to its high surface hydroxyl content and the formed Schottky junction after Au loading. These results suggested that noble metal modification is a promising way to synthesize photocatalysts with both high activity and visible light sensitivity.     

Realization of an extremely low reflectance surface based on InP porous nanostructures for application to photoelectrochemical solar cells

Extremely low reflectance was obtained from InP porous nanostructures in UV, visible, and near-infrared ranges. Porous samples were electrochemically prepared on which 130-nm-diameter nanopores were formed in a straight, vertical direction and were laterally separated by 50-nm-thick InP nanowalls. The reflectance strongly depended on the surface morphology. The lowest reflectance of 0.1% in the visible light range was obtained after the irregular top layer had been completely removed. Superior photoelectrochemical properties were obtained on the InP porous structures due to two unique features: the large surface area inside pores, and the large photon absorption enhanced on the low reflectance surface.     

Flexible a‐Si:H Solar Cells with Spontaneously Formed Parabolic Nanostructures on a Hexagonal‐Pyramid Reflector

Flexible amorphous silicon (a‐Si:H) solar cells with high photoconversion efficiency (PCE) are demonstrated by embedding hexagonal pyramid nanostructures below a Ag/indium tin oxide (ITO) reflector. The nanostructures constructed by nanoimprint lithography using soft materials allow the top ITO electrode to spontaneously form parabolic nanostructures. Nanoimprint lithography using soft materials is simple, and is conducted at low temperature. The resulting structure has excellent durability under repeated bending, and thus, flexible nanostructures are successfully constructed on flexible a‐Si:H solar cells on plastic film. The nanoimprinted pyramid back reflector provides a high angular light scattering with haze reflectance >98% throughout the visible spectrum. The spontaneously formed parabolic nanostructure on the top surface of the a‐Si:H solar cells both reduces reflection and scatters incident light into the absorber layer, thereby elongating the optical path length. As a result, the nanopatterned a‐Si:H solar cells, fabricated on polyethersulfone (PES) film, exhibit excellent mechanical flexibility and PCE increased by 48% compared with devices on a flat substrate.