CdS quantum dot sensitized nanocrystalline Gd-doped TiO2 thin films for photoelectrochemical solar cells

CdS quantum dot sensitized Gd-doped TiO₂ nanocrystalline thin films have been prepared by chemical method. X-ray diffraction analysis reveals that TiO₂ and Gd-doped TiO₂ nanocrystalline thin films are of anatase phase. The absorption spectra revealed that the absorption edge of CdS quantum dot sensitized Gd-doped TiO₂ thin films shifted towards longer wavelength side (red shift) when compared to that of CdS quantum dot sensitized TiO₂ films. CdS quantum dots with a size of 5 nm have been deposited onto Gd-doped TiO₂ film surface by successive ionic layer adsorption and reaction method and the assembly of CdS quantum dot with Gd-doped TiO₂ has been used as photo-electrode in quantum dot sensitized solar cells. CdS quantum dot sensitized Gd-doped TiO₂ based solar cell exhibited a power conversion efficiency of 1.18 %, which is higher than that of CdS quantum dot sensitized TiO₂ (0.91 %).     

Doping-free fabrication of silicon thin films for schottky solar cell

Thin film Schottky solar cells were fabricated without doping processes, which may provide an alternative approach to the conventional thin film solar cells in the n-i-p configuration. A thin Co layer was coated on a substrate, which worked as a back contact metal and then Si film was grown above it. Deposition condition may modulate the Si film structure to be a fully amorphous Si (a-Si) or a mixing of microcrystalline Si (mc-Si) and a-Si. A thin Au layer was deposited above the grown Si films, which formed a Schottky junction. Two types of Schottky solar cells were prepared on a fully a-Si film and a mixing of mc-Si and a-Si film. Under one sun illumination, the mixing of mc-Si and a-Si device provided 35% and 68.4% enhancement in the open circuit voltage and fill factor compared to that of the amorphous device.     

Low-cost fabrication of Cu2ZnSnS4 thin films for solar cell absorber layers

A new and low-cost chemical method is used to fabricate Cu₂ZnSnS₄ (CZTS) thin films by annealing Cu–Sn metallic inks with spin-coating ZnO layers under H₂S. The obtained pure phase and smooth CZTS thin films are characterized by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). Further, the CZTS thin films are grown on n-type Si substrates to form proto-type CZTS/Si heterojunction solar cells that have photovoltaic properties, indicating the promising application of CZTS as the absorber layers in Si-based heterojunction solar cells.     

柔性染料敏化太阳能电池TiO2薄膜的低温制备技术

简要介绍了柔性染料敏化太阳能电池的特点,综述了柔性染料敏化太阳能电池中TiO2纳米晶半导体薄膜光电极的低温制备技术.     

Different TiO2 nanotubes for back illuminated dye sensitized solar cell: fabrication,characterization and electrochemical impedance properties of DSSCs

In the present work we reported the fabrication of different TiO₂ nanotube arrays (TiO₂ NTs) by anodization method. When used in dye-sensitized solar cells, the TiO₂ NTs prepared in the two-step anodization process (2-step TiO₂ NTs) showed better efficiency than those of TiO₂ NTs prepared in one step anodization process (1-step TiO₂ NTs). The 2-step TiO₂ NTs show a remarkable efficiency of 1.56 %. This is higher than those of TiO₂ NTs prepared in one step anodization process. Electrochemical impedance spectroscopy has been performed for qualitative analysis of charge transport process in dye-sensitized solar cells.     

大规模真空蒸镀二氧化钛薄膜及其表征

采用大型真空镀膜设备在玻璃基底上蒸镀二氧化钛(TiO2)薄膜,并对TiO2薄膜进行了SEM、AFM、XRD、紫外可见光吸收光谱、亲水性的测试及分析,探讨了退火温度对薄膜性能的影响.结果表明制备的TiO2薄膜具有良好的均匀性.在室温条件下,TiO2薄膜具有无定型的结构;在300～500℃的条件下,TiO2薄膜退火2h后以锐铁矿晶型为主,600℃退火的TiO2薄膜明显向金红石型转变.随退火温度的升高,薄膜对紫外光和可见光的吸收有明显提高,并出现了明显的红移现象.另外,亲水性也随退火温度的升高而变强,500和600℃退火的TiO2薄膜表面出现超亲水性.     

Direct assembly of preformed nanoparticles and graft copolymer for the fabrication of micrometer-thick, organized TiO2 films: high efficiency solid-state dye-sensitized solar cells

Solid-state dye-sensitized solar cell with 7.1% efficiency at 100 mW/cm(2) is reported, one of the highest observed for N719 dye. Excellent performance was achieved via a graft copolymer-templated, organized mesoporous TiO(2) film with a large surface area using spindle-shaped, preformed TiO(2) nanoparticles and solid polymer electrolyte.     

Preparation and characterization of nanostructured ZnO thin films for photoelectrochemical splitting of water

Nanostructured zinc oxide thin films (ZnO) were prepared on conducting glass support (SnO₂: F overlayer) via sol-gel starting from colloidal solution of zinc acetate 2-hydrate in ethanol and 2-methoxy ethanol. Films were obtained by spin coating at 1500 rpm under room conditions (temperature, 28–35°C) and were subsequently sintered in air at three different temperatures (400, 500 and 600°C). The evolution of oxide coatings under thermal treatment was studied by glancing incidence X-ray diffraction and scanning electron microscopy. Average particle size, resistivity and bandgap energy were also determined. Photoelectrochemical properties of thin films and their suitability for splitting of water were investigated. Study suggests that thin films of ZnO, sintered at 600°C are better for photoconversion than the films sintered at 400 or 500°C. Plausible explanations have been provided.     

Ti O2纳米管阵列基底退火温度对CdSe/Ti O2异质结薄膜光电化学性能的影响

通过电化学沉积法以TiO2纳米管阵列(TNTs)为基底制备CdSe/TiO2异质结薄膜。研究TiO2纳米管阵列基底不同退火温度(200,350,450,600℃)对CdSe/TiO2异质结薄膜光电化学性能的影响。采用SEM,XRD,UV-Vis,电化学测试等方法对样品的微观形貌、晶体结构、光电化学性能等进行表征。结果表明:立方晶型的CdSe纳米颗粒均匀沉积在TiO2纳米管阵列管口及管壁上。TiO2纳米管阵列未经退火及退火温度为200℃时,为无定型态,在TiO2纳米管阵列上沉积的CdSe纳米颗粒数量少,尺寸小,异质结薄膜光电性能较差,光电流几乎为零。随着退火温度升高到350℃,TiO2纳米管阵列基底开始向锐钛矿转变;且沉积在TiO2纳米管上的CdSe颗粒增多,尺寸增大,光电化学性能提高。退火温度为450℃时光电流值达到最大,为4.05mA/cm^2。当退火温度达到600℃时,TiO2纳米管有金红石相出现,CdSe颗粒变小,数量减少,光电化学性能下降。     

Preparation and characterization of radio-frequency-sputtered Ba2Si2TiO8 thin films

Radio-frequency-sputtered barium titanium silicate (BST, Ba₂Si₂TiO₈) thin films were grown on crystalline Si (100) substrates and were characterized using wavelength-dispersive spectrometry (WDS), X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM), and diagonal techniques for dielectric properties. The chemical compositions of the films increasingly deviated from stoichiometry with film thickness. At the initial stage of deposition the grain configuration is dependent on the Si substrate texture. XRD analysis indicates that the BST films deposited at an optimum substrate temperature of 845 °C were strongly c-axis oriented, and that the film orientation is manipulated by substrate temperature and supersaturation. The corresponding film-growth rate in the direction normal to the film surface at 845 °C was 1.95 nm min^–1 at the initial stage, and decreased with sputtering time. The as-deposited films have a room-temperature bulk resistivity of 1.8 ×10⁷ m in the direction of thickness and an isotropic surface resistivity of 1.5×10³ m. The high-frequency relative dielectric constant, 0.05 at frequencies higher than 9 MHz, is lower than that of many typical piezoelectric materials. The high-frequency impedance character is typical of piezoelectric materials, giving a minimum impedance frequency of 9.0 MHz and a serial resonant frequency at about 9.5 MHz.     

有序大孔TiO2双层膜的设计合成及其在染料敏化太阳能电池中的应用

以垂直沉积法制备的聚苯乙烯(polystyrene,PS)胶体晶体为模板,钛酸四异丙酯为钛源,通过浸渍-煅烧工艺制备了具有分层次有序结构的大孔TiO2双层膜,并作为光阳极应用于染料敏化太阳能电池(dye-sensitized solar cells,DSSCs)。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)、紫外-可见漫反射光谱仪和氮气吸附-脱附分析仪等手段对样品进行了表征。结果表明,有序大孔TiO2薄膜较好地复制了PS模板的三维有序结构,且有较大的比表面积。光电性能测试结果表明,与以纯P25薄膜为光阳极的DSSCs相比,有序大孔TiO2双层膜为光阳极能够明显提高DSSCs的光电转换效率,可从4.16%提高到6.08%。该类型分层次有序结构大孔TiO2双层膜在DSSCs中具有重要的潜在应用价值。     

Preparation and characterization of TiO2 thin films by the sol-gel process

Titanium dioxide (TiO₂) thin films have been prepared on microscope slide by the sol-gel process. The preparation of covering solution is investigated with the method of orthogonal experimental design, and the heat treatment temperature and time, which influenced on the films properties are discussed. And the TiO₂ thin films had been studied by the means of differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM).     

Antimony-incorporated TiO2 thin films: preparation and optical and electrical characteristics

Antimony-incorporated TiO₂ thin films were prepared using the spray-pyrolysis technique. The optical characteristics (percentage transmittance, refractive index, extinction coefficient) and the film thickness were investigated. The resistivity of the prepared samples was measured, and the effect of Sb concentration and film thickness on the measured parameters was discussed. The effect of Sb on the band-gap was also studied.     

Nanoparticulate magnetite thin films as electrode materials for the fabrication of electrochemical capacitors

Magnetite nanoparticles in stable colloidal suspension were prepared by the co-precipitation method. Nanoparticulate magnetite thin films on supporting stainless steel plates were prepared by drop-coating followed by heat treatment under controlled conditions. The effects of calcination temperature and atmosphere on the microstructure and electrochemical properties of nanoparticulate magnetite thin films were investigated. Nanoparticulate magnetite thin films prepared under optimized conditions exhibited a specific capacitance value of 82 F/g in mild aqueous 1.0 M Na₂SO₄ solution. Due to their high charge capacity, good cycling reversibility, and stability in a mild aqueous electrolyte, nanoparticulate magnetite thin films appear to be promising electrode materials for the fabrication of electrochemical capacitors.     

FeS2 quantum dots sensitized nanostructured TiO2 solar cell: photoelectrochemical and photoinduced absorption spectroscopy studies

Thin films of nanostructured TiO₂ have been modified with FeS₂ (pyrite) nano-particles by a low temperature chemical reaction of iron pentacarbonyl with sulfur in xylene. Quantum size effects are manifested by the observation of a blue shift in both absorption and photocurrent action spectra. PIA (Photoinduced absorption spectroscopy), where the excitation is provided by a square-wave modulated (on/off) monochromatic light emitting diode, is a multipurpose tool in the study of dye-sensitized solar cells. Here, PIA is used to study quantum-dot modified TiO₂ nanostructured electrodes. The PIA spectra obtained give evidence for long-lived photoinduced charge separation: electrons are injected into the metal oxide and holes are left behind in the FeS₂ quantum dot. Time-resolved PIA shows that recombination between electrons and holes occurs on a millisecond timescale. The Incident-Photon-to-Current Efficiency of about 23 % was obtained at 400 nm excitation. The performances of TiO₂ electrodes modified with FeS₂ are relatively low, which is explained by the presence of FeS₂ phases other than the photoactive pyrite phase, as follows from the XRD spectrum.     

Nb-doped TiO2 thin films for photovoltaic applications

Polycrystalline titania and Nb:TiO₂ thin films were deposited by RF magnetron sputtering. The influence of post-deposition annealing in vacuum and hydrogen atmosphere on the structure, morphology, oxidation states and optical properties was studied by X-ray diffraction, atomic force microscopy, XPS and UV–VIS spectroscopy. The heat treatment of titanium dioxide thin films in vacuum and H₂ atmosphere induces structural and morphological changes. The band gap narrowing was observed for the transparent as-deposited Nb:TiO₂ films, while annealing at 420 °C in H₂ atmosphere resulted in an enhancement of the electrical conductivity. Further on, TiO₂/p-CdTe photovoltaic devices with efficiency of 1.8% were fabricated and their characteristic ‘enhancement’ is discussed.     

CdS多晶薄膜的制备及性质研究

分别采用近空间升华法和电子束蒸发法在透明导电玻璃和普通载玻片上制备了硫化镉(CdS)多晶薄膜.对制备样品的表征结果表明:(1)两种方法制备样品都沿(002)晶向择优生长,属于六方相多晶结构,但择优取向度不同;(2)CdS薄膜表面连续而致密,粒径均匀,但两种工艺制备样品的S:Cd原子比有较大差异;(3)CdS薄膜的光能隙在2.39～2.44eV之间,电子束蒸发制备样品光能隙稍小.分析认为,两种方法制备样品的上述差异可能与衬底温度、沉积时间及成膜机制的不同相关.     

Solvothermal synthesis of CuInS2 powders and CuInS2 thin films for solar cell application

In this study, a facile solvothermal method was developed to prepare CuInS₂ powders and CuInS₂ thin films. The CuInS₂ powders and CuInS₂ thin films were prepared by solvothermal route using the precursor of Copper (II) chloride, indium (III) nitrate, thiourea, oxalic acid, hexadecyl trimethyl ammonium bromide and ethanol. The morphology, crystallographic structure, chemical composition and optical band gap of CuInS₂ powders and CuInS₂ thin films were investigated using scanning electronic microscope (SEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS) and UV–vis spectroscopy. The results reveal that both CuInS₂ powders and CuInS₂ thin films are in chalcopyrite phase. The CuInS₂ powders are mainly composed of flower-like microspheres. Both microstructure of the sphere surface and diameter of sphere are affected by indium nitrate concentration in precursors. The CuInS₂ thin films are composed of a large number of uniform flower-like nanosheets, and the nanosheets become smaller in size and denser in distribution density with increasing concentration of thiourea. The optical band gap is found to be 1.44 and 1.52 eV for CuInS₂ powders and CuInS₂ thin films, respectively. The deposition mechanism of the CuInS₂ is discussed.