PLD法制备基于缓冲层的ZnO薄膜及纳米棒研究进展

综述了脉冲激光沉积(PLD)法基于缓冲层制备ZnO薄膜及ZnO纳米棒的研究进展,分析了缓冲层对于生长高质量ZnO薄膜及纳米棒的作用,得到结论:引入缓冲层可以减少沉积物与衬底晶格失配以及热膨胀系数不匹配的问题。     

生长时间对氧化锌纳米杆形貌的影响

采用旋涂法在洗净的玻璃衬底上制备了醋酸锌薄膜,并进一步在空气中退火获得了氧化锌(ZnO)薄膜,X射线衍射分析显示退火后获得的ZnO薄膜具有c轴(002)择优取向生长特性.通过水热法以ZnO薄膜为种子层,生长了ZnO纳米杆阵列.研究了在相同的ZnO种子层、前驱液浓度和生长温度条件下,不同生长时间对ZnO纳米杆形貌的影响.扫描电子显微镜照片显示,随着生长时间的增加,ZnO纳米杆阵列的生长具有阶段性规律,并且在经过52h生长后得到了顶端中心被溶解的ZnO纳米管.分析认为该现象和前驱液中Zn2+离子和OH-离子的浓度变化有关,同时也和ZnO的非极性结构有关.     

一维ZnO纳米/微米棒的制备及光学性能研究

采用溶胶-凝胶法,以六水硝酸锌和乙二醇单甲醚为主要原料,在SiO2玻璃衬底上旋涂一层致密的ZnO籽晶,用水热法,通过对ZnO籽晶层面朝下和朝上分别制备了ZnO纳米棒和微米棒。研究了不同生长液浓度对ZnO纳米/微米棒的形貌和光学性能的影响。结果表明,ZnO纳米棒直径约在Φ(60~90)nm之间,长度约为1 600nm,微米棒直径约Φ(1~4)μm,长度约8~14μm;随着生长液浓度的增加,ZnO纳米棒越致密,而ZnO微米梭生长成ZnO微米棒;ZnO纳米/微米棒的光致发光(PL)光谱强度随着生长液浓度的增加逐渐增强     

两步法生长ZnO纳米棒的结构及其发光特性

应用两步法在玻璃衬底上制备了高度取向的ZnO纳米棒,并研究了衬底和反应时间等参数对其结构及发光特性的影响。从样品的扫描电镜(SEM)图中发现,利用脉冲激光沉积(PLD)方法在玻璃衬底上生长一层ZnO薄膜作为修饰层,可以明显提高水热法生长的ZnO纳米棒的结晶质量。样品的SEM和光致发光(PL)谱表明,在有ZnO修饰层的玻璃衬底上生长的ZnO纳米棒分布均匀,排列致密,取向性好;缺陷发光的发光强度约是激子发光峰的2倍,且随着反应时间增长,样品的缺陷发光增强而激子发光减弱。     

ZnO纳米棒薄膜光学性能的系统研究

采用简化的种子层制备工艺在ITO基底上制备了ZnO种子层,并使用化学溶液沉积法制备了高度取向的ZnO纳米棒阵列。采用XRD和SEM对ZnO纳米棒的结构和形貌进行表征,并对样品的光学性能进行了测试。测试结果表明,所制备的ZnO纳米棒为c轴择优取向的六角纤锌矿结构,直径为66~122nm可控,且排列紧密,形貌规整。光学性能测试结果表明,吸收光谱在375nm附近表现出强烈的紫外吸收边是由于禁带边吸收引起的;反射光谱具有一定的周期振荡性,可用于薄膜厚度的估算;光致发光谱在378nm附近有很强的紫外发射峰;增大生长液浓度和高温退火可降低缺陷发光,改善结晶质量。     

酞菁染料ZnPc和Q-PbS复合敏化纳米晶ZnO薄膜电极的研究

利用溶胶-凝胶旋涂镀膜法结合热处理工艺在FTO玻璃上制备了ZnO薄膜,并通过X射线衍射(XRD)、扫描电子镜(SEM)对其晶相及表面形貌进行了表征;以酞菁染料ZnPc和窄禁带半导体PbS量子点(Q-PbS)为敏化剂,分别制备了FTO/ZnO/ZnPc电极、FTO/ZnO/Q-PbS电极和FTOZnO/Q-PbS/ZnPc电极,结果表明,ZnPc和Q-PbS对ZnO纳米颗粒膜产生了良好的敏化作用,且两者的复合敏化效果最好;制备了FTO/ZnO/Q-PbS/ZnPc为光阳极的染料敏化太阳能电池(DSSC),在模拟太阳光下,电池的开路电压为304mV,短路电流为1.42mA,光电转换效率为0.696%,填充因子为0.348。     

籽晶层热处理温度对ZnO纳米棒阵列性能的影响

以不同热处理温度下制备的ZnO籽晶层为基底,采用水热法生长ZnO纳米棒阵列,对制备得到的ZnO纳米棒阵列的相结构和微观形貌以及发光特性进行了表征,分析了籽晶层热处理温度对ZnO纳米棒阵列性能的影响机理,发现在籽晶层热处理温度为450℃时,生长得到的ZnO纳米棒阵列空间取向最优,发光性能最好。     

籽晶层退火温度对ZnO纳米棒形貌及发光特性的影响

以不同退火温度处理后的ZnO籽晶层为基底,采用水热法生长了ZnO纳米棒阵列。对制备得到的ZnO纳米棒阵列的形貌、结构以及发光特性进行了表征,分析了籽晶层的退火温度对ZnO纳米棒阵列的形貌及发光性质的影响,发现通过调节籽晶层的退火温度,可以控制ZnO纳米棒的大小及密度,并发现在经400℃退火后的籽晶层上生长的ZnO纳米棒阵列形貌最佳,发光性能最优。     

ZnO纳米棒的电沉积生长方法研究

用含有硝酸锌(Zn(NO3)2)和六次甲基四胺(HMTA,C6H12N4)的电解液,在低温环境下采用阴极电沉积法在ITO玻璃上成功合成了氧化锌(ZnO)纳米棒阵列。系统研究了电压、前驱物(Zn2+)浓度、温度和种子层等参数对ZnO纳米棒形貌结构的影响,实现了ZnO纳米棒的可控制备。结果表明,在有种子层的情况下,当电压为-0.9V、Zn2+浓度为0.01M、温度为75℃条件下生长的ZnO纳米棒c-轴择优取向好、尺寸均匀(80~100nm),且在380~750nm的可见光波长范围内的透射率达到80%。     

TiO_2/SrTiO_3薄膜电极制备及其光电化学性能研究

采用商用P25TiO2为原料制备纳米多孔TiO2电极,用水热法在多孔TiO2表面包覆SrTiO3。采用X射线衍射仪、扫描电子显微镜及紫外-可见光谱仪对TiO2/SrTiO3薄膜电极进行表征。探讨了水热反应温度对TiO2/SrTiO3薄膜电极组装染料敏化太阳能电池(DSSC)的光电化学性能影响。结果表明:在纳米多孔TiO2电极表面生成了均匀的SrTiO3包覆层,且SrTiO3包覆的样品吸收边有红移;与TiO2薄膜电极相比,不同水热反应温度下制备的TiO2/SrTiO3薄膜电极组装DSSC的光电转换效率均有所提高,180℃时全光转换效率提高了24%。     

Coral‐shaped ZnO nanostructures for dye‐sensitized solar cell photoanodes

A highly efficient ZnO photoanode for dye‐sensitized solar cells was successfully grown by a simple, low cost, and scalable method. A nanostructured coral‐shaped Zn layer was deposited by sputtering onto fluorine‐doped tin oxide/glass slices at room temperature and then thermally oxidized in ambient atmosphere. Stoichiometry, crystalline phase, quality, and morphology of the film were investigated, evidencing the formation of a highly porous branched nanostructure, with a pure wurtzite crystalline structure. ZnO‐based dye‐sensitized solar cells were fabricated with customized microfluidic architecture. Dye loading on the oxide surface was analyzed with ultraviolet‐visible spectroscopy, and the dependence of the cell efficiency on sensitizer incubation time and film thickness was studied by current‐voltage electrical characterization, incident photon‐to‐electron conversion efficiency, and impedance spectroscopy measurements, showing the promising properties of this material for the fabrication of dye‐sensitized solar cell photoanodes with a solar conversion efficiency up to 4.58%. Copyright © 2012 John Wiley & Sons, Ltd.     

Polydisperse Aggregates of ZnO Nanocrystallites: A Method for Energy‐Conversion‐Efficiency Enhancement in Dye‐Sensitized Solar Cells

ZnO films consisting of either polydisperse or monodisperse aggregates of nanocrystallites were fabricated and studied as dye‐sensitized solar‐cell electrodes. The results revealed that the overall energy‐conversion efficiency of the cells could be significantly affected by either the average size or the size distribution of the ZnO aggregates. The highest overall energy‐conversion efficiency of ～4.4% was achieved with the film formed by polydisperse ZnO aggregates with a broad size distribution from 120 to 360 nm in diameter. Light scattering by the submicrometer‐sized ZnO aggregates was employed to explain the improved solar‐cell performance through extending the distance travelled by light so as to increase the light‐harvesting efficiency of photoelectrode film. The broad distribution of aggregate size provides the ZnO films with both better packing and an enhanced ability to scatter the incident light, and thus promotes the solar‐cell performance.     

Effect of Eosin Y Dye on Electrical Properties of ZnO Film Synthesized by Sol–Gel Technique

This paper presents preparation of zinc oxide (ZnO) nanoparticles by the sol–gel technique. ZnO films were prepared by the doctor-blade method, and the resulting films were sensitized with eosin Y (EY) by immersing them in a solution of EY dye in ethanol. The prepared samples were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transmission infrared spectroscopy, and ultraviolet (UV)–visible spectroscopy. The monodispersed ZnO nanocrystals possess a wurtzite hexagonal structure with diameter of ～7 nm to 17 nm as observed by XRD and TEM analyses. The absorption spectrum of EY-dye-sensitized ZnO (ZnO/EY) film is slightly broadened, with a red-shift in the peak position compared with the absorbance spectrum of the dye in ethanol. Measurements of electrical parameters such as dark conductivity and photoconductivity were carried out at different temperatures. Transient photoconductivity was also studied at different temperatures to investigate the photoconduction mechanism. The photosensitivity of the ZnO/EY film is higher than that of the ZnO film. Hall measurements show n-type behavior for both samples. The visible absorption spectrum and high photosensitivity of the ZnO/EY films support their potential use as photoanode materials in dye-sensitized solar cells and optoelectronic devices.     

Spray deposited ZnO and Ga doped ZnO based DSSC with bromophenol blue dye as sensitizer: Efficiency analysis through DFT approach

Dye sensitized solar cells based on spray deposited ZnO and Ga doped ZnO (GZO) thin film were fabricated with Bromophenol Blue as the photo sensitizer. XRD results show the hexagonal wurtzite phase of ZnO and GZO thin films with c-axis growth orientation, and the diminished crystalline nature of GZO thin film as the effect of doping. FE-SEM results revealed the morphology induced internal light interaction capability of GZO thin film for better harvesting of photon energy. Photovoltaic studies showed that the DSSC fabricated with GZO thin film has obtained enhanced power conversion efficiency (1%) than the ZnO thin film based DSSC (0.2%), as a result of Ga doping. To investigate the obtained photovoltaic performance of the device, the electronic properties of Bromophenol Blue dye were theoretically analyzed with Density Functional Theory (DFT) study.     

ZnO nanorod arrays as an antireflective coating for Cu(In,Ga)Se2 thin film solar cells

A ZnO nanorod antireflective coating has been prepared on Cu(In,Ga)Se₂ thin film solar cells. This coating leads to a decrease of the weighted global reflectance of the solar cells from 8.6 to 3.5%. It boosts the solar cells short‐circuit current up to 5.7% without significant effect on their open‐circuit voltage and fill factor (FF), which is comparable to a conventional optimized single layer MgF₂ antireflective coating. The ZnO nanorod antireflective coating was electrochemically prepared from an aqueous solution at 80°C. The antireflective capability of ZnO nanorod arrays (ZNAs) may be further improved by optimization of growth conditions and their geometry. Copyright © 2010 John Wiley & Sons, Ltd.     

Characteristics of Polyaniline/Si Heterojunction Solar Cell By Electrochemical Dye Sensitization

Using the electrochemical polymerization dye sensitization （ECDS） method, polyaniline （PAn）, which is used as top region material in solar cells, is sensitized with direct blue dye（DS）, and sensitized Al grid/DS-PAn/n-Si/Al heterojunction solar cells is prepared by ECDS. Influences of the ECDS on the absorption spectrum and the junction characteristics of the solar cell were discussed, and the output characteristics were measured. The results show that the absorption spectrum of the sensitized PAn films is much wider and stronger in Vis-range; the diode quality factor is about 6.3 and the height of latent barrier potential of p-n junction is 0.89 eV; the short-circuit current and the conversion efficiency of sensitized DS- PAn/Si heterojunction solar cells are greatly improved, which the short-circuit current can increase 6 times, the fill factor is 57% and the efficiency can reach 1.42 % under the illumination of 37.2 W/m^2 , respectively.     

Transparent,Double‐Sided,ITO‐Free,Flexible Dye‐Sensitized Solar Cells Based on Metal Wire/ZnO Nanowire Arrays

Transparent, double‐sided, flexible, ITO‐free dye‐sensitized solar cells (DSSCs) are fabricated in a simple, facile, and controllable way. Highly ordered, high‐crystal‐quality, high‐density ZnO nanowire arrays are radially grown on stainless steel, Au, Ag, and Cu microwires, which serve as working electrodes. Pt wires serve as the counter electrodes. Two metal wires are encased in electrolyte between two poly(ethylene terephthalate) (PET) films (or polydimethylsiloxane (PDMS) films) to render the device both flexible and highly transparent. The effect of the dye thickness on the photovoltaic performance of the DSSCs as a function of dye‐loading time is investigated systematically. Shorter dye‐loading times lead to thinner dye layers and better device performance. A dye‐loading time of 20 min results in the best device performance. An oxidation treatment of the metal wires is developed effectively to avoid the galvanic‐battery effect found in the experiment, which is crucial for real applications of double‐metal‐wire DSSC configurations. The device shows very good transparency and can increase sunlight use efficiency through two‐sided illumination. The double‐wire DSSCs remain stable for a long period of time and can be bent at large angles, up to 107°, reversibly, without any loss of performance. The double‐wire‐PET, planar solar‐cell configuration can be used as window stickers and can be readily realized for large‐area‐weave roll‐to‐roll processing.