硅纳米线阵列的制备及其光电应用

近年来,硅纳米线阵列在宽波段、宽入射角范围内优异的减反射性能及其在光电领域的巨大应用前景引起了相关研究者的广泛关注。本文综述了国内外硅纳米线阵列的制备及其在光电应用方面的最新研究进展。关于硅纳米线阵列的制备方法,主要从"自下而上"和"自上而下"两大类出发,分别阐述了模板辅助的化学气相沉积法、化学气相沉积结合Langmuir-Blodgett技术法和金属催化化学刻蚀法,其中重点介绍了目前使用最为广泛且操作简单的金属催化化学刻蚀法的步骤、机理及控制参数。关于硅纳米线阵列在光电领域的应用,主要阐述了硅纳米线阵列在光电探测器、常规太阳能电池、光电化学太阳能电池、光催化分解水制氢、光催化降解有机污染物方面的应用。最后,从硅纳米线阵列在实际应用中面临的提高光电转换效率和避免硅纳米线阵列腐蚀以提高器件的稳定性等问题出发,展望了硅纳米线阵列的表面修饰及修饰后的性能研究是未来硅纳米线阵列光电应用研究的主要方向之一。     

硅衬底上聚丙烯酰胺/氧化锌纳米线薄膜蓝色发光二极管

采用高分子络合软模板法利用高分子络合和低温氧化烧结反应,在硅衬底上自组装生长出顶面平滑具有六角柱形结构的ZnO纳米线,并基于此聚丙烯酰胺/ZnO纳米线体系构筑了聚合物基ZnO纳米线发光二极管器件,在相对低的阈值电压下实现了常温常压下电场驱动的蓝色发射光,并且其发光颜色可由其应用的激励电压方便地调控.几乎垂直排列的ZnO纳米线/高分子薄膜在器件中被作为发射层.该方法使用聚合物作为LED器件的粘结剂和发光层的分散介质,稳定了硅衬底上埋置在聚合物薄膜中的ZnO纳米线准阵列并对ZnO纳米晶的表面起钝化作用,防止发光猝灭.结果表明,新技术是一种低成本制备ZnO基紫外/蓝色发光材料的工艺,并且减少了以往工艺中要求ZnO薄膜p型掺杂的麻烦.     

ZnO纳米线/棒阵列的水热法制备及应用研究进展

氧化锌(ZnO)纳米线/棒阵列的质量决定了所构建光电器件的性能. 为了制备出比表面积更大、垂直性更好以及无根部融合的高质量ZnO纳米线/棒阵列, 本文概述了近几年两步水热法可控制备ZnO纳米线/棒阵列的研究进展, 分别探讨了种子层、生长液和生长方法对纳米线/棒阵列形貌的影响, 详细分析了氨水、六次甲基四胺和聚乙烯亚胺对于促进纳米线/棒阵列生长的作用机理, 提出了通过微流控技术可控制备ZnO纳米线阵列提高纳米线生长效率的方法. 最后介绍了ZnO纳米线/棒阵列的形貌对于提高染料敏化太阳能电池、纳米发电机、气体传感器和场发射器件性能的重要作用, 并对未来两步水热法制备ZnO纳米线/棒阵列的发展趋势进行了展望.     

硅纳米线阵列电极作为细胞色素c传感器的研究

利用化学刻蚀法由p型硅片制备了硅纳米线阵列,经过表面去氧化层处理后,制备了检测蛋白质细胞色素c的电化学传感器.实验表明,硅纳米线阵列电极对细胞色素c有良好的电化学响应,并且在低浓度条件下具备线性响应的特点.根据与未经表面处理的硅纳米线阵列电极的实验结果相对比,提出了细胞色素c所具备的羧基末端与硅纳米线阵列电极表面的Si-H相互作用从而改善传感性能的检测机理.     

取向纳米ZnO/Cu_2O异质结阵列的制备及光电特性

以水热合成法制备的一维取向n型ZnO纳米线阵列为衬底,采用电化学沉积法在其上沉积生长一层p型Cu2O半导体包覆层,制备出了新型ZnO/Cu2O异质结纳米线阵列光敏器件.利用XRD、SEM、TEM、XPS、PL及光响应特性等测试方法对样品的形貌、晶体结构、化学成分及光电特性进行了分析表征.研究了生长条件对ZnO/Cu2O异质结纳米线阵列各种特性的影响.研究发现,适宜的沉积电压和沉积时间是保证ZnO/Cu2O异质结光敏器件具有适宜厚度核壳包覆层及较好光响应特性的关键因素.研究结果为ZnO及Cu2O半导体材料在光敏器件中的应用提供了实验基础.     

模板法制备枝状Pt纳米线

一维纳米材料的制备是近年来纳米材料的研究热点. 利用具有纳米尺度的孔洞阵列模板沉积各种材料构筑纳米线的方法具有制备简便和成本较低等优点[1,2]. 常用的模板有多孔阳极氧化铝(AAO)、多孔硅和聚合物等, 其中AAO模板具有耐高温, 绝缘性好, 孔洞分布均匀, 孔径、孔深大小可控等特点, 是模板法研究的热点. 通过模板法电化学沉积制备各种金属纳米线已有很多报道[3～8], 本研究小组也曾报道了模板法电化学沉积Au等纳米线的制备及性质[9～12], 但用该方法制备的金属纳米线都为单一的线状结构. 组成当代大规模集成电路的基本器件一般具有3个或3个以上的电极. 单一的线状结构纳米线, 不能满足纳米电子学对纳米材料和纳米器件性能研究的需要. 在纳米器件的特性研究和探索中, 枝状或Y形纳米结的制备有重要的意义, 它是纳米器件从理论到实用化的必备条件. Sui等[13]用模板法成功制备了枝状碳纳米管, 但用AAO模板制备枝状金属纳米线的研究至今还未见报道. 本文通过控制铝片的阳极氧化条件, 先制备出具有分枝状孔洞结构的AAO模板, 再用电化学法沉积金属Pt, 实现了枝状Pt纳米线的可控生长. 这对其它金属枝状纳米线的制备以及进一步掺杂、构筑纳米原型器件等具有显著的实用价值.     

基于宏观金属辅助化学刻蚀制备硅纳米线的研究

分别利用镀银的硅衬底和铂丝电极作为原电池反应中的阴极和阳极,基于金属辅助化学刻蚀采用宏观原电池的方法制备硅纳米线,深入研究了该法制备硅纳米线阵列的机理。通过改变电连接、镀银、刻蚀参数、硅衬底和光照等实验条件,系统地研究了所得硅纳米线形貌与其对应短路电流的关系,实验发现短路电流与硅纳米线长度有一定的对应关系。文章中所提出的模型旨在从根本上解决金属辅助化学刻蚀制备硅纳米线的机理。最后对这种方法所具有的潜在应用价值进行了展望和讨论。     

高效传质与电子转移的全纳米线光催化燃料电池自驱动净水同步产氢

分别以三维分级碳布基底上组装的TiO₂纳米线阵列和铂化的硅纳米线阵列作为光阳极和光阴极,构建了具有高效传质和电子转移特征的全纳米线光催化燃料电池。在光照作用下,光阳极微流道内的光生空穴能有效氧化降解有害污染物,这同时增强了光电子还原水产氢的活性。与传统的平面式光电极相比,全纳米线光催化燃料电池在不需要外部偏压条件下即可高效降解模拟印染废水和同步生成氢气新能源。     

高效传质与电子转移的全纳米线光催化燃料电池自驱动净水同步产氢

分别以三维分级碳布基底上组装的TiO₂纳米线阵列和铂化的硅纳米线阵列作为光阳极和光阴极,构建了具有高效传质和电子转移特征的全纳米线光催化燃料电池。在光照作用下,光阳极微流道内的光生空穴能有效氧化降解有害污染物,这同时增强了光电子还原水产氢的活性。与传统的平面式光电极相比,全纳米线光催化燃料电池在不需要外部偏压条件下即可高效降解模拟印染废水和同步生成氢气新能源。     

湿化学法制备硅纳米线阵列及其光电化学产氢性能分析

为了探究不同方法条件下制备的硅纳米线阵列电极产氢性能异同,文中分别采用了两步金属辅助催化无电刻蚀法、一步金属辅助催化无电刻蚀法以及阳极氧化法来制备硅纳米线阵列用作为光电分解水电池光阴极材料。通过FESEM、XRD和UVVis-IR DRS等手段对实验样品的形貌、晶型、减反性表征,发现相比于其他2种方法所得硅纳米线样品,两步金属辅助催化无电刻蚀法制备的硅纳米线结构晶型保持更好,表面缺陷更少。光电化学测试表明两步金属辅助催化无电刻蚀法制备的硅纳米线光电化学性能表现最优,其光电流密度值是一步法的4倍,阳极氧化法的40倍;转移电荷电阻仅是一步法制备的硅纳米线阵列阻值的1/3,阳极氧化法制备的1/1 000。     

Rectangular bunched rutile TiO2 nanorod arrays grown on carbon fiber for dye-sensitized solar cells

Because of their special application in photovoltaics, the growth of one-dimensional single-crystalline TiO(2) nanostructures on a flexible substrate is receiving intensive attention. Here we present a study of rectangular bunched TiO(2) nanorod (NR) arrays grown on carbon fibers (CFs) from titanium by a "dissolve and grow" method. After a corrosion process in a strong acid solution, every single nanorod is etched into a number of small nanowires. Tube-shaped dye-sensitized solar cells are fabricated by using etched TiO(2) NRs-coated CFs as the photoanode. An absolute energy conversion efficiency of 1.28% has been demonstrated under 100 mW cm(-2) AM 1.5 illumination. This work demonstrates an innovative method for growing bunched TiO(2) NRs on flexible substrates that can be applied in flexible devices for energy harvesting and storage.     

聚吡咯纳米线凝胶的模板制备及储能与电化学传感性能

以配位聚合物凝胶为模板, 构筑均一的聚吡咯纳米线网络, 聚合后经简单处理除去模板, 得到性能优异的聚吡咯凝胶. 结果表明, 模板法合成的聚吡咯凝胶为由均一纳米线组成的三维网络结构, 具有良好的力学性能、 较大的比表面积及优异的电化学特性, 在0.28 A/g电流密度下, 比电容可达450 F/g, 在2.8 A/g电流密度下充放电1000次, 比电容仍可保持88.6%. 聚吡咯纳米线网络凝胶经葡萄糖氧化酶负载后得到柔性传感电极, 对低浓度(0.2 mmol/L)的葡萄糖具有快速响应性能, 有望用于超级电容器及生物电化学传感器等领域.     

Experimental study of the depth influence on the band broadening effect in a cyclo-olefin polymer column containing an array of ordered pillars

An experimental study of a micromachined non-porous pillar array column performance under non-retentive conditions is presented. The same pillar structure has been fabricated in cyclo-olefin polymer (COP) chips with three different depths via hot embossing and pressure-assisted thermal bonding. The influence of the depth on the band broadening along with the already known contribution arising from the top and bottom cover plates has been studied. The experimental results exhibit reduced plate heights as low as 0.2, which are in agreement with the previous experimental work. Moreover, the constant values of the reduced Van Deemter expression are also in accordance with the previous studies. A more exhaustive study of the C-term band broadening is also presented, showing that comparing the space between the pillars with different open tubular rectangular channels offers a good estimation of the C-term band broadening that is obtained experimentally. These experimental results, hence, confirm that micromachined pillar array columns fabricated in COP can achieve the same performance as the ones fabricated in silicon for the presently studied pillar channel design.     

Characterization and field emission properties of ZnMgO nanowires fabricated by thermal evaporation process

In this paper, we investigate the roles of gold catalyst using modified thermal evaporation set-up in the growth process of ZnMgO nanowires. ZnMgO nanowires are fabricated on silicon substrates using different thickness of gold catalyst. A simple horizontal double-tube system along with chemical vapor diffusion of the precursors, based on Fick’s first law, is used to grow the ZnMgO nanowires. Field emission scanning electron microscopy images show that the ZnMgO nanowires are tapered. The optical properties of the ZnMgO nanowires are characterized by room temperature photoluminescence (PL) measurements. The PL studies demonstrate that the ZnMgO nanowires grown using this method have good crystallinity with excellent optical properties and have a larger band-gap in comparison to the pure ZnO nanowires. Field emission characterization shows that the turn-on field for the nanowires grown on the thinner gold film is lower than those grown on the thicker gold film.     

喷涂法制备高效率三元体系聚合物太阳能电池

采用喷涂技术制备了能量转化效率为9.06%的三元体系聚合物太阳能电池,该太阳能电池在卷对卷印刷和规模化生产中具有极大的应用潜力。     

Dye-sensitized solar cells based on anatase TiO2 nanoparticle/nanowire composites

Dye-sensitized solar cells were fabricated based on the composites of anatase TiO2 nanoparticles and single crystalline anatase TiO2 nanowires. Nanoparticle/nanowire composites can possess the advantages of both building blocks, i.e., the high surface area of nanoparticle aggregates and the rapid electron transport rate and the light scattering effect of single-crystalline nanowires. Three different composites were prepared with 5 wt %, 20 wt %, and 77 wt % nanowires, respectively. The performances of composite solar cells were compared with pure nanoparticle cells at a series of film thickness. With low nanowire concentrations (5 wt % and 20 wt %), the composite films maintain similar specific surface area as the pure nanoparticle films, while the composite cells show higher short-circuit current density and open-circuit voltage. An enhancement of power efficiency from 6.7% for pure nanoparticle cells to 8.6% for the composite cell with 20 wt % nanowires has been achieved under 1 Sun AM1.5 illumination (100 mW/cm2). For the composite film with 77 wt % nanowires, the nanowires became the major phase. Their less compact packing resulted in significant decrease of the specific surface area, and thus the current density. However, with the increase of film thickness, the current density showed a continuous increase in the whole thickness range up to 17 microm, indicating the improved electron diffusion length due to the formed nanowire network. The nanowires also helped to preserve crack-free thick films. These results show that employing nanoparticle/nanowire composites represents a promising approach for further improving the efficiencies of sensitized solar cells.     

Control of superhydrophilicity/superhydrophobicity using silicon nanowires via electroless etching method and fluorine carbon coatings

Surface roughness is promotive of increasing their hydrophilicity or hydrophobicity to the extreme according to the intrinsic wettability determined by the surface free energy characteristics of a base substrate. Top-down etched silicon nanowires are used to create superhydrophilic surfaces based on the hemiwicking phenomenon. Using fluorine carbon coatings, surfaces are converted from superhydrophilic to superhydrophobic to maintain the Cassie-Baxter state stability by reducing the surface free energy to a quarter compared with intrinsic silicon. We present the robust criteria by controlling the height of the nanoscale structures as a design parameter and design guidelines for superhydrophilic and superhydrophobic conditions. The morphology of the silicon nanowires is used to demonstrate their critical height exceeds several hundred nanometers for superhydrophilicity, and surpasses a micrometer for superhydrophobicity. Especially, SiNWs fabricated with a height of more than a micrometer provide an effective means of maintaining superhydrophilic (<10°) long-term stability.     

Experimental study of the retention properties of a cyclo olefin polymer pillar array column in reversed-phase mode

Experimental measurements to study the retention capacity and band broadening under retentive conditions using micromachined non-porous pillar array columns fabricated in cyclo olefin polymer are presented. In particular, three columns with different depths but with the same pillar structure have been fabricated via hot embossing and pressure-assisted thermal bonding. Separations of a mixture of four coumarins using varying mobile phase compositions have been monitored to study the relation between the retention factor and the ratio of organic solvent in the aqueous mobile phase. Moreover, the linear relation between the retention and the surface/volume ratio predicted in theory has been observed, achieving retention factors up to k=2.5. Under the same retentive conditions, minimal reduced plate height values of h(min)=0.4 have been obtained at retention factors of k=1.2. These experimental results are compared with the case of non-porous and porous silicon pillars. Similar results for the plate heights are achieved while retention factors are higher than the non-porous silicon column and considerably smaller than the porous pillar column, given the non-porous nature of the used cyclo olefin polymer. The feasibility of using this polymer column as an alternative to the pillar array silicon columns is corroborated.     

喷墨打印技术制备聚合物太阳能电池的研究进展

聚合物太阳能电池具有成本低、质量轻、容易制备大尺寸器件等优势,是太阳能电池研究中最为活跃的领域之一。喷墨打印技术作为新的成膜技术,具有材料利用率高、快速、可柔性加工等优点,已被用于聚合物太阳能电池的制备,发展潜力巨大。综述了聚合物太阳能电池、喷墨打印技术和喷墨打印技术制备聚合物太阳能电池的研究进展,同时对聚合物太阳能电...     

Structural, magnetic, and magnetoresistive properties of electrodeposited Ni5Zn21 alloy nanowires

Ni5Zn21 alloy nanowires were fabricated through template-assisted electrochemical deposition method. The morphology and microstructures of as-deposited nanowires were determined by field-emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), electron diffraction (ED), and electron probe microanalysis (EPMA). The accurate composition was measured via induced coupling plasma atomic emission spectroscopy. SEM results show that Ni5Zn21 nanowires are deposited in most of the nanopores of the template, and they are continuous and dense throughout the whole length. The XRD result demonstrates that the nanowires are mainly composed of a cubic gamma phase Ni5Zn21 alloy, but there also exists a trace of Zn-rich eta phase. HRTEM and ED reveal that the alloy nanowires are polycrystalline with the crystallite size of several tens of nanometers. EPMA of a single nanowire illustrates that there exist Ni-rich microzones in as-deposited nanowires. Subsequent magnetic measurements of the array also confirmed the existence of them. In addition, it can be further inferred that the shape of Ni-rich microzones is probably barlike or disklike, from the anisotropy of zero field cooling/field cooling (ZFC/FC) curves as well as the vortex magnetization behavior of the Ni5Zn21 nanowire array. The low-temperature magnetoresistance of the Ni5Zn21 nanowire array was also measured. Giant magnetoresistance instead of anisotropic magnetoresistance is suggested to be responsible for contributing to the magnetoresistance.