P3HT/CdS/TiO2/ZnO一维有序核壳式纳米棒阵列的构制及其在杂化太阳电池中的应用研究

采用恒电位法在铟锡氧化物导电玻璃(ITO)上制备了高度有序一维ZnO纳米棒阵列,将ZnO纳米棒阵列在TiO2溶胶中采用提拉法制备出了一维TiO2/ZnO核壳式纳米棒阵列.在一维TiO2/ZnO核壳式纳米棒阵列上电沉积CdS纳米晶得到一维CdS/TiO2/ZnO核壳式纳米棒阵列,然后在一维CdS/TiO2/ZnO核壳式纳米棒阵列上电沉积聚3-己基噻吩(P3HT)薄膜得到P3HT/CdS/TiO2/ZnO核壳式纳米结构薄膜.以该纳米结构薄膜电极为光阳极制备出新型纳米结构杂化太阳电池,研究了该类电池的光电转换性能,初步探讨了该类电池的工作机理.     

ZnO纳米棒阵列在TiO2介孔薄膜上的生长及其表征

通过低温水热法成功地将ZnO纳米棒阵列定向生长在了介孔锐钛矿TiO2纳米晶薄膜上,并主要利用X射线衍射、场发射扫描电子显微镜和光致发光光谱等对其进行了表征。所制备的纳米棒具有六边形的端面,纳米棒的尺寸及端面边长分布范围窄,并且沿c轴方向(002)表现出了明显的择优化生长。此外,相比于玻璃基底或TiO2纳米颗粒薄膜,生长在介孔TiO2薄膜上的ZnO纳米棒阵列表现出了较好的取向生长,表明基底的表面结构和组成对ZnO纳米棒阵列的生长有显著的影响。根据基底有序的多孔结构,讨论了纳米棒阵列可能的生长机理。所得到的ZnO纳米棒阵列在室温下分别表现出了以370 nm为中心的强近紫外光和以530 nm为中心的弱绿光两条荧光谱带。     

纳米结构ZnO在TiO_2薄膜上的电化学沉积及其表征

在三电极体系中,以硝酸锌水溶液作为电解液,采用阴极还原电沉积法成功实现了一维纳米结构ZnO阵列在TiO2纳米粒子/ITO导电玻璃薄膜基底上的沉积,并通过XRD、SEM、EDS和PL光谱等方法对样品进行了表征.重点研究了薄膜基底、电解液浓度、沉积时间、六次亚甲基四胺(HMT)的引入对ZnO沉积及其发光性质的影响.结果显示:与ITO玻璃基底相比,ZnO更易于在TiO2纳米粒子薄膜上实现电化学沉积.ZnO属于六方晶系的铅锌矿结构,并且沿着c-轴方向表现出明显的择优化生长,以形成垂直于基底的ZnO纳米棒阵列.延长沉积时间、增加电解液浓度和引入一定量的HMT等均对ZnO的生长有促进作用,进而使其纳米棒的结晶度和取向程度提高,进而解释了所得的薄膜分别约在375和520nm处表现出ZnO的强而窄的带边紫外光发射峰和弱而宽的表面态绿光发射带.     

光电化学水氧化用多孔单晶金红石TiO2纳米棒阵列光阳极的设计和构建

光电化学电池(如染料敏化太阳能电池、量子点敏化太阳能电池以及光电化学水分解电池)是实现太阳能转化及存储的有效手段之一.其中,光电极是光电化学电池的核心组成部分,它集光吸收、光生电荷输运及转移等决定光转化效率的关键过程于一身,因此构筑高活性半导体光电极以实现高效太阳能转化利用引起研究者广泛关注.多孔TiO2纳米颗粒堆垛薄膜光阳极因具有大的比表面积,可提供更多的染料(量子点)担载和反应活性位点,在光电化学电池中表现出优异活性而被广泛研究.然而, TiO2纳米颗粒间大量存在的晶界对光生电荷有较强的散射作用,降低了光生电荷的收集效率.英国牛津大学Snaith研究小组利用模板辅助水热过程首次获得了(001)晶面占优的多孔单晶锐钛矿TiO2微米颗粒,这种多孔单晶TiO2微米颗粒在具有大比表面积的同时,其单晶结构还能有效去除晶界对电荷的散射作用,因而具有优异的电荷输运特性.利用这种多孔单晶TiO2微米颗粒组建的光阳极用于染料敏化太阳能电池中,展现出优异的太阳能光电转化性能.受该工作启发,各种形貌的多孔单晶TiO2微米颗粒作为光催化剂和光电化学分解水用光阳极材料被广泛研究,并表现出优异活性.在单晶微米颗粒堆垛成的薄膜光电极中,虽然单个单晶微米颗粒中晶界对电荷的散射作用被有效抑制,但是单晶颗粒间的晶界仍然存在并影响光生电荷的收集效率.为了彻底抑制晶界对光生电荷的散射作用,每个单晶颗粒都应该贯穿整个薄膜,例如一维TiO2纳米棒单晶阵列薄膜.虽然一维单晶阵列薄膜能够有效提高光生电荷的收集效率,但相对于多孔薄膜具有较小的比表面积,限制了担载染料(量子点)和反应位点的数量.为了增大TiO2单晶纳米棒阵列薄膜的比表面积,目前主要的手段包括调控纳米棒长径比、表面修饰TiO2纳米颗粒以及二次生长构建TiO2枝晶阵列.本文首次提出通过制备多孔单晶TiO2纳米棒单晶阵列薄膜来获得高比表面积和高光生电荷收集效率的光阳极,提高光电化学电池的效率.在透明导电薄膜(FTO)表面利用水热生长TiO2纳米棒阵列薄膜之前,预先在FTO基体上沉积一层SiO2球密堆模板, TiO2纳米棒单晶阵列在从FTO表面向上生长过程中,会将SiO2球模板包裹进TiO2纳米棒中,再通过碱溶液将SiO2球模板溶解,首次在FTO基体上原位生长出多孔单晶TiO2纳米棒阵列薄膜.将所得多孔单晶金红石TiO2纳米棒阵列薄膜作为光电化学分解水电池光阳极,其光电化学分解水活性相对于实心单晶金红石TiO2纳米棒阵列提高了2.6倍.多孔单晶金红石TiO2纳米棒阵列光阳极性能的提升可归因于：(1)多孔结构赋予多孔单晶金红石TiO2纳米棒阵列薄膜更大的比表面积,可提供更多的反应活性位点;(2)多孔结构能够有效缩短单晶金红石TiO2纳米棒中光生电荷体相输运距离,提高光生电荷的收集效率;(3)多孔结构通过对光多次反射吸收可有效增强光吸收,产生更多光生电荷参与水分解反应;(4)在制备过程中引入Si掺杂,导致多孔单晶金红石TiO2纳米棒带隙扩大了0.1 eV,带隙增大归因于导带位置负移0.1 eV,光生电子具有更强的还原能力,光电流起始电位相应负移约0.1 V.     

Au/ZnO/TiO_2复合薄膜的制备及光电转换性质

以含有Au和ZnO纳米颗粒的氢氧化钛溶胶作为成膜液,通过浸渍-提拉及灼烧处理在导电玻璃表面制备Au/ZnO/TiO2复合薄膜.利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)等方法对所得产物进行表征.结果表明,Au和ZnO纳米颗粒均匀地分布在多孔TiO2薄膜上,通过TiO2、ZnO和Au三组分的协同效应促进了光吸收和电荷分离,使Au/ZnO/TiO2复合薄膜具有较好的光电转换性质,可用作太阳能电池材料.     

ZnO/TiO2纳米管复合材料的制备及光电化学性能研究

采用电化学阳极氧化法制备TiO2纳米管,然后用光化学沉积法在TiO2纳米管表面沉积ZnO纳米颗粒制备ZnO/TiO2纳米复合材料。对样品进行了Raman谱、XRD和SEM表征,通过测定光电流-时间(I-t)和开路电压-时间(OCPT)曲线对ZnO/TiO2纳米复合材料的光电化学性能进行研究。结果表明,沉积ZnO没有改变TiO2的相结构;复合ZnO提高了TiO2的光电性能;在Zn(NO3)2浓度为10-3 mol.L-1的条件下制得的ZnO/TiO2纳米复合材料具有较好的光电性能。     

液相沉积法制备ZnO/CdS复合纳米棒阵列薄膜及其光电性质

采用两步化学溶液沉积法在氧化铟锡(ITO)导电玻璃衬底上制备了ZnO/CdS复合纳米棒阵列薄膜.利用X射线衍射(XRD)仪、扫描电子显微镜(SEM)、紫外-可见(UV-Vis)吸收分光光度计、荧光(PL)光谱仪及表面光电压谱(SPS)研究了不同CdS沉积时间对复合薄膜的晶体结构、形貌、光电性质的影响.研究结果表明:ZnO纳米棒阵列表面包覆CdS纳米颗粒后,其吸收光谱可拓展到可见光区;与吸收光谱相对应在可见光区出现新的光电压谱响应区,这一现象证实,通过与CdS复合可显著提高ZnO纳米棒阵列在可见光区的光电转换性能;随着CdS纳米颗粒沉积时间的延长,复合纳米棒阵列薄膜在大于383nm波长区域的光电压强度逐渐减弱,而在小于383nm波长区域的光电压强度逐渐增强.用两种不同的电荷产生和分离机制对这一截然相反的光响应过程进行了详细的讨论和解释.     

P3HT修饰一维有序壳核式CdS/ZnO纳米棒阵列复合膜的光电化学性能

采用电化学方法在铟锡氧化物(ITO)导电玻璃上制备了高度有序的ZnO纳米棒阵列, 在ZnO纳米棒阵列上先后电化学沉积CdS纳米晶膜及聚3-己基噻吩(P3HT)薄膜得到P3HT修饰的一维有序壳核式CdS/ZnO纳米阵列结构, 并通过扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、能量散射X射线(EDX)等表征手段证实了该结构的形成. 以此纳米结构薄膜为光阳极组装新型半导体敏化太阳电池, 研究了CdS纳米晶膜的厚度和P3HT薄膜的沉积对电池光伏性能的影响, 初步探讨了电荷在电池结构中的传输机理, 结果表明, CdS纳米晶膜和P3HT薄膜的沉积有效地拓宽了光阳极的光吸收范围, 实验中电池的光电转换效率最高达到1.08%.     

Ag掺杂对n-ZnO纳米棒/p-GaN异质结结构和发光性能的影响

利用简单的水热合成法在p-GaN薄膜上制备了Ag掺杂的一维ZnO纳米棒(ZnO NRs),并且研究了Ag掺杂对于ZnO NRs结构和形貌以及n-ZnO NRs/p-GaN异质结发光特性的影响。结果表明,不同Ag掺杂浓度的ZnO纳米棒截面均呈六边形的棒状结构,且纳米棒的取向垂直于衬底;XRD分析结果表明,随着Ag掺杂浓度的增加,ZnO纳米棒(0002)晶面的峰位向衍射角减小的方向移动,表明Ag+置换了ZnO晶格中的部分Zn2+后使其晶格常数略增加;随着Ag掺杂浓度的增加,ZnO纳米棒近带边发光峰发生一定的红移并且强度逐渐减弱,黄带发光峰逐渐增强,n-ZnO NRs/p-GaN异质结具有更好的传输效率。     

化学溶液沉积法制备单分散氧化锌纳米棒阵列

在由溶胶凝胶法制备的纳米ZnO薄膜基底上, 采用化学溶液沉积法制备了单分散、高度取向的ZnO纳米棒阵列膜. 通过控制纳米ZnO薄膜的制备工艺, 可以调节氧化锌纳米棒的直径. 利用FESEM, TEM, HRTEM, SAED和XRD表征了氧化锌纳米棒阵列的形貌和晶体结构. ZnO纳米棒的室温PL谱具有很高的紫外带边发射峰, 在可见光波段无发射峰, 表明该方法制备的ZnO纳米棒晶体结构完整, 晶体中O空位的浓度很低.     

电沉积法制备固态染料敏化太阳能电池

本文采用一步电化学沉积的方法在导电玻璃上先后沉积了ZnO/染料复合薄膜以及CuSCN薄层,实现仅以电沉积法制备结构为ZnO/染料/CuSCN的固态染料敏化太阳能电池,电池的光电转换效率达到0.1%.在电沉积CuSCN前,脱附电沉积制备的ZnO/染料复合薄膜中的染料以形成多孔ZnO薄膜,然后通过染料再吸附得到染料敏化ZnO纳晶多孔薄膜.在电沉积过程中,ZnO和CuSCN的晶体尺寸、晶体取向和膜层形貌都可以进行比较精准的控制.探讨了影响沉积薄膜形貌和光电转换效率的因素,如旋转圆盘电极的旋转速度、电沉积温度以及染料敏化剂的选择.本文报道的低温电沉积制备全固态太阳能电池的方法为制备柔性染料敏化太阳能电池提供了一种新的思路.     

Highly efficient plastic substrate dye-sensitized solar cells using a compression method for preparation of TiO(2) photoelectrodes

The efficiency of a plastic-substrate dye-sensitized solar cell was much improved by a new method consisting of a press method without heat treatment, light confinement effect of TiO(2) film and water-based TiO(2) paste; this device shows the highest light-to-electrical energy conversion efficiency based on plastic-substrate dye-sensitized solar cells, 7.4% under 100 mW cm(-2) (1 sun) AM1.5 illumination.     

Modified phthalocyanines for efficient near-IR sensitization of nanostructured TiO(2) electrode

A zinc phthalocyanine with tyrosine substituents (ZnPcTyr), modified for efficient far-red/near-IR performance in dye-sensitized nanostructured TiO(2) solar cells, and its reference, glycine-substituted zinc phthalocyanine (ZnPcGly), were synthesized and characterized. The compounds were studied spectroscopically, electrochemically, and photoelectrochemically. Incorporating tyrosine groups into phthalocyanine makes the dye ethanol-soluble and reduces surface aggregation as a result of steric effects. The performance of a solar cell based on ZnPcTyr is much better than that based on ZnPcGly. Addition of 3alpha,7alpha-dihydroxy-5beta-cholic acid (cheno) and 4-tert-butylpyridine (TBP) to the dye solution when preparing a dye-sensitized TiO(2) electrode diminishes significantly the surface aggregation and, therefore, improves the performance of solar cells based on these phthalocyanines. The highest monochromatic incident photo-to-current conversion efficiency (IPCE) of approximately 24% at 690 nm and an overall conversion efficiency (eta) of 0.54% were achieved for a cell based on a ZnPcTyr-sensitized TiO(2) electrode. Addition of TBP in the electrolyte decreases the IPCE and eta considerably, although it increases the open-circuit photovoltage. Time-resolved transient absorption measurements of interfacial electron-transfer kinetics in a ZnPcTyr-sensitized nanostructured TiO(2) thin film show that electron injection from the excited state of the dye into the conduction band of TiO(2) is completed in approximately 500 fs and that more than half of the injected electrons recombines with the oxidized dye molecules in approximately 300 ps. In addition to surface aggregation, the very fast electron recombination is most likely responsible for the low performance of the solar cell based on ZnPcTyr.     

Preparation of a nanoporous CaCO3-coated TiO2 electrode and its application to a dye-sensitized solar cell

A nanoporous CaCO3 overlayer-coated TiO2 thick film was prepared by the topotactic thermal decomposition of Ca(OH)2, and its performance as an electrode of a dye-sensitized solar cell was investigated. As compared to bare TiO2, nanoporous CaCO3-coated TiO2 provided higher specific surface area and, subsequently, a larger amount of dye adsorption; this in turn increased short-circuit current (Jsc). Furthermore, the CaCO3 coating demonstrated increased impedance at the TiO2/dye/electrolyte interface and increased the lifetime of the photoelectrons, indicating the improved retardation of the back electron transfer, which increases Jsc, open-circuit voltage (Voc), and fill factor (ff). Thereby, the energy conversion efficiency (eta) of the solar cell improved from 7.8 to 9.7% (an improvement of 24.4%) as the nanoporous CaCO3 layer was coated onto TiO2 thick films.     

Fast electron transport in metal organic vapor deposition grown dye-sensitized ZnO nanorod solar cells

The electron transport in dye-sensitized solar cells with a MOCVD (metal organic vapor deposition)-grown ZnO nanorod array (ZnO-N) or a mesoporous film prepared from ZnO colloids (ZnO-C) as the working electrode was compared. The electrodes were of similar thickness (2 mum) and sensitized with zinc(II) meso-tetrakis(3-carboxyphenyl)porphyrin, while the electrolyte was I(-)/I(3)(-) in 3-methoxypropionitrile. Electron transport in the ZnO-C cells was comparable with that found for colloidal TiO(2) films (transport time approximately 10 ms) and was light intensity dependent. Electron transport in solar cells with ZnO-N electrodes was about 2 orders of magnitude faster ( approximately 30 mus). Thus, the morphology of the working ZnO electrode plays a key role for the electron transport properties.     

Deposition of a thin film of TiOx from a titanium metal target as novel blocking layers at conducting glass/TiO2 interfaces in ionic liquid mesoscopic TiO2 dye-sensitized solar cells

In dye-sensitized TiO2 solar cells, charge recombination processes at interfaces between fluorine-doped tin oxide (FTO), TiO2, dye, and electrolyte play an important role in limiting the photon-to-electron conversion efficiency. From this point of view, a high work function material such as titanium deposited by sputtering on FTO has been investigated as an effective blocking layer for preventing electron leakage from FTO without influencing electron injection. X-ray photoelectron spectroscopy analysis indicates that different species of Ti (Ti4+, Ti3+, Ti2+, and a small amount of Ti0) exist on FTO. Electrochemical and photoelectrochemical measurements reveal that thin films of titanium species, expressed as TiOx, work as a compact blocking layer between FTO and TiO2 nanocrystaline film, improving Voc and the fill factor, finally giving a better conversion efficiency for dye-sensitized TiO2 solar cells with ionic liquid electrolytes.     

Triton X-100对染料敏化太阳电池性能影响的研究

采用无水相体系的胶体通过丝网印刷工艺制备TiO2薄膜电极,研究发现曲拉通(TritonX-100)可以明显改变TiO2电极显微结构,且对染料敏化太阳电池的性能影响显著.过少或过多的曲拉通都将导致开路电压、短路电流、填充因子以及效率的降低.由3gP25粉末配制的胶体中,曲拉通适宜的加入量约为0.8mL.     

TiO(2) porous electrodes with hierarchical branched inner channels for charge transport in viscous electrolytes.

Titanium dioxide (TiO(2)) photoelectrodes with micro/nano hierarchical branched inner channels have been prepared by an electrohydrodynamic (EHD) technique and assembled to form dye-sensitized solar cells (DSSCs). Excellent penetration of ionic-liquid electrolytes and enhanced light harvesting in the longer wavelength region are realized within the composite-structure electrode, thus a better fill factor (ff) of 75.3 % and higher conversion efficiency (eta) of 7.1 % are obtained for viscous ionic-liquid electrolytes compared to pure nanostructured films. Hierarchical branched channels in the photoanodes can efficiently improve the transport properties of redox-active species in viscous electrolytes, which is demonstrated by electrical impedance spectroscopy (EIS). The incident monochromatic photon-to-electron conversion efficiency (IPCE) shows that enhanced light scattering in the composite film is of benefit for light harvesting and thus for solar energy conversion efficiency.     

二氢吲哚类染料用于染料敏化太阳能电池光敏剂的比较

采用密度泛函理论(DFT)和含时密度泛函理论(TD-DFT)对四种二氢吲哚染料进行研究, 从中筛选出相对优秀的染料敏化太阳能电池光敏剂. 对前线分子轨道的计算表明, 二氢吲哚染料的前线分子轨道结构非常有利于染料激发态向TiO2电极的电子注入. 对真空中的紫外和可见光吸收光谱的计算表明, 二氢吲哚染料的吸收光谱与太阳辐射光谱匹配较好. 对染料分子的能级计算表明, 二氢吲哚染料的能级结构比较适合于I-/I-3作电解液的TiO2纳米晶太阳能电池的光敏剂. 二氢吲哚染料最低未占据分子轨道(LUMO) 能级均比TiO2晶体导带边能级高, 能够保证激发态染料分子高效地向TiO2电极转移电子. 二氢吲哚染料最高占据分子轨道(HOMO)的能级比I-/I-3能级低, 保证了失去电子的染料分子能够顺利地从电解液中得到电子. 与实验数据比较, 得出在提高染料敏化太阳能电池转换效率方面, 对染料的关键要求是LUMO能级的位置. 染料分子的稳定性是染料敏化太阳能电池使用寿命的关键因素. 通过对化学键键长的比较表明, 二氢吲哚染料的分子稳定性基本相同. 对计算结果的分析表明, 二氢吲哚染料1(ID1)的LUMO能级最高, 分子稳定性最好, 在酒精溶液中的吸收光谱与太阳辐射光谱匹配很好, 在同类染料中是较好的染料敏化太阳能电池光敏剂.     

Enhancement of the efficiency of dye-sensitized solar cell with multi-wall carbon nanotubes/polythiophene composite counter electrodes prepared by electrodeposition

For the purpose of increasing the energy conversion efficiency of dye-sensitized solar cells (DSSCs), multi-wall carbon nanotube (MWCNT)/polythiophene (PTh) composite film counter electrode has been fabricated by electrophoresis and cyclic voltammetry (CV) in sequence. The morphology and chemical structure have been characterized by transmission electron microscopy (TEM), scanning electron microscope (SEM), and Raman spectroscopy respectively. The overall energy conversion efficiency of the DSSC employing the MWCNT/PTh composite film has reached 4.72%, which is close to that of the DSSC with a platinum (Pt) counter electrode (5.68%). Compared with a standard DSSC with MWCNT counter electrode whose efficiency is 2.68%, the energy conversion efficiency has been increased by 76.12% for the DSSC with MWCNT/PTh counter electrode. These results indicate that the composite film with high conductivity, high active surface area, and good catalytic properties for I₃⁻ reduction can potentially be used as the counter electrode in a high-performance DSSC.