Triton-X mediated interconnected nanowalls network of cadmium sulfide thin films via chemical bath deposition and their photoelectrochemical performance

Thin films of cadmium sulfide (CdS) have been wet chemically deposited onto fluorine-doped tin oxide (FTO) coated conducting glass substrates by using non-ionic surfactant; Triton-X 100. An aqueous solution contains cadmium sulphate as a cadmium and thiourea as sulphur precursor. Ammonia used as a complexing agent. The results of measurements of the x-ray diffraction, Raman spectroscopy, optical spectroscopy, energy dispersive spectroscopy, scanning electron microscopy, Brunauer Emmett Teller (BET) surface areas and atomic force microscopy were used for the characterization of the films. These results revealed that the films are polycrystalline, consisting of CdS cubic phase. The films show a direct band gap with energy 2.39 eV. The films show interconnected nanowalls like morphology with well-defined surface area. Finally, the photoelectrochemical (PEC) performance of Triton-X mediated CdS thin film samples were studied. The sample shows photoelectrochemical (PEC) performance with maximum short circuit current density (J_sc) 1.71 mA/cm² for larger area (1 cm²) solar cells.     

Synthesis of ZnO nanorods and their application in quantum dot sensitized solar cells

ZnO nanorod thin films of different thicknesses and CdS quantum dots have been prepared by chemical method. X-ray diffraction pattern reveals that the CdS quantum dot and ZnO nanorods are of hexagonal structure. Field emission scanning electron microscope images show that the diameter of hexagonal shaped ZnO nanorods ranges from 110 to 200 nm and the length of the nanorod vary from 1.3 to 4.7 μm. CdS quantum dots with average size of 4 nm have been deposited onto ZnO nanorod surface using successive ionic layer adsorption and reaction method and the assembly of CdS quantum dot with ZnO nanorod has been used as photo-electrode in quantum dot sensitized solar cells. The efficiency of the fabricated CdS quantum dot-sensitized ZnO nanorod-based solar cell is 1.10 % and is the best efficiency reported so far for this type of solar cells.     

Indium and aluminium-doped ZnO thin films deposited onto FTO substrates: nanostructure,optical, photoluminescence and electrical properties

The microstructure, optical, photoluminescence and electrical properties of ZnO based films deposited onto FTO glass substrates by ultrasonic spray pyrolysis have been investigated. For comparison and a better understanding of physical properties of indium- and aluminum-doped ZnO and undoped ZnO thin films, X-ray diffraction analysis, photoluminescence spectra, optical, SEM texture and electrical conductivity analyses were performed. The AZO and IZO films exhibit the nanofiber structure with diameters 260 and 400 nm. X-ray diffraction showed all samples to be polycrystalline with hexagonal ZnO. The optical band gaps of the films were varied by Al and In dopants. The photoluminescence spectra of the films show a weak broad in the visible range and shifted to green emission for indium doping and to the green blue emission for aluminum as dopant. The width of the PL spectra for aluminum-doped films is too large compared to those of the indium-doped ones. The electrical conductivity of the ZnO film changes with Al and In dopants. The position of donor levels changes with In and Al dopants and approaches the conduction band level with the metal dopants. The obtained results suggest that the metal doping has a clear effect upon the growth, optical, photoluminescence and electrical conductivity properties of the ZnO films.     

CdS‐Encapsulated TiO2 Nanotube Arrays Lidded with ZnO Nanorod Layers and Their Photoelectrocatalytic Applications

A novel TiO₂ nanotube array/CdS nanoparticle/ZnO nanorod (TiO₂ NT/CdS/ZnO NR) photocatalyst was constructed which exhibited a wide‐absorption (200–535 nm) response in the UV/Vis region and was applied for the photoelectrocatalytic (PEC) degradation of dye wastewater. This was achieved by chemically assembling CdS into the TiO₂ NTs and then constructing a ZnO NR layer on the TiO₂ NT/CdS surface. Scanning electron microscopy (SEM) results showed that a new structure had been obtained. The TiO₂ NTs looked like many “empty bottles” and the ZnO NR layer served as a big lid. Meanwhile the CdS NPs were encapsulated between them with good protection. After being sensitized by the CdS NPs, the absorption‐band edge of the obtained photocatalyst was obviously red‐shifted to the visible region, and the band gap was reduced from its original 3.20 eV to 2.32 eV. Photoelectric‐property tests indicated that the TiO₂ NT/CdS/ZnO NR material maintained a very high PEC activity in both the ultraviolet (UV) and the visible region. The maximum photoelectric conversion efficiencies of TiO₂ NT/CdS/ZnO NR were 31.8 and 5.98 % under UV light (365 nm) and visible light (420–800 nm), respectively. In the PEC oxidation, TiO₂ NT/CdS/ZnO NR exhibited a higher removal ability for methyl orange (MO) and a high stability. The kinetic constants were 1.77×10^?4 s^?1 under UV light, which was almost 5.9 and 2.6 times of those on pure TiO₂ NTs and TiO₂ NT/ZnO NR, and 2.5×10^?4 s^?1 under visible light, 2.4 times those on TiO₂ NT/CdS.     

CdS/FTO thin film electrodes deposited by chemical bath deposition and by electrochemical deposition: A comparative assessment of photo-electrochemical characteristics

CdS thin films have been deposited onto FTO/glass substrates by two different techniques, electrochemical deposition (ECD) and chemical bath deposition (CBD). Feasibility of using these two film types in photoelectrochemical processes has been critically investigated here. The films were comparatively characterized by a number of techniques (solid state absorption spectra, solid state photoluminescence spectra, XRD and SEM). PEC characteristics of the electrodes, including current density–voltage (J–V) plots, conversion efficiency (η), stability and fill-factor (FF) were then studied. The results show that both systems involved nano-sized CdS particles living in coagulates. The ECD was thinner and more uniform than the CBD system. The CBD films were more effective in PEC processes than the ECD counterparts. Effect of annealing on characteristics of both electrode systems has been investigated. Annealing enhanced both film characteristics, but the CBD was affected to a higher extent, and the annealed CBD film was more effective than the ECD counterpart.     

Influence of Ga dopant on photoelectrochemical characteristic of Ga‐doped ZnO thin films deposited by sol–gel spin‐coating technique

In this study, Ga‐doped ZnO thin films were prepared using sol–gel technique via spin‐coating method. The effect of Ga‐doping dopant (0, 1, 2 and 3 at.%) on microstructural, optical, electrical and photoelectrochemical (PEC) characteristics have been investigated. The spin‐coating was repeated six times, and as‐obtained thin films were then annealed at 500 °C for 1 h in vacuum. After annealing, all samples revealed single phase of hexagonal ZnO polycrystalline structure with a main peak of (002) in X‐ray diffraction (XRD) pattern. Raman spectra show that the vibration strength of E₂ is highly decreased by Ga doping. Thicknesses of all samples were ~300 nm measured via scanning electron microscopy (SEM) cross‐section images and alpha‐step. The optical band gap and resistivity of samples were in the range of 3.24 to 3.28 eV and 102 to 9 Ohm cm, respectively. Resulting from PEC response, the 2 at.% Ga‐doped ZnO thin film has a better PEC performance with photocurrent density of ~0.14 mA/cm² at 0.5 V versus saturated calomel electrode (SCE) under illumination with the intensity of 100 mW/cm². This value was about seven times higher than the un‐doped film (reference sample). Observed higher photocurrent density was likely because of a suitable Ga‐doping concentration causing a lower resistivity. Copyright © 2016 John Wiley & Sons, Ltd.     

CdS nanocrystallites sensitized ZnO nanorods with plasmon enhanced photoelectrochemical performance

A novel architecture of CdS/ZnO nanorods with plasmonic silver (Ag) nanoparticles deposited at the interface of ZnO nanorods and CdS nanocrystallites, was designed as a photoanode for solar hydrogen generation, with photocurrent density achieving 4.7 mA/cm² at 1.6 V (vs. RHE), which is 8 and 1.7 times as high as those of pure ZnO and CdS/ZnO nanorod films, respectively. Additionally, with optical absorption onset extended to ～660 nm, CdS/Ag/ZnO nanorod film exhibits significantly increased incident photo-to-current efficiency (IPCE) in the whole optical absorption region, reaching 23.1% and 9.8% at 400 nm and 500 nm, respectively. The PEC enhancement can be attributed to the one-dimensional ZnO nanorod structure maintained for superior charge transfer, and the extended visible-light absorption of CdS nanocrystallites. Moreover, the incorporated plasmonic Ag nanoparticles could further promote the interfacial charge carrier transfer process and enhance the optical absorption ability, due to its excellent plasmon resonance effect.     

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%.     

CdS nanocrystallites sensitized ZnO nanorods with plasmon enhanced photoelectrochemical performance

A sandwiched structure of CdS/Ag/ZnO nanorod photoanode exhibits greatly enhanced photoelectrochemical activity for solar hydrogen generation, due to synergistic effect of CdS nanocrystallites and plasmonic Ag nanoparticles for the enhanced optical absorption and the promoted charge carrier separation.     

Sn掺杂ZnO纳米针的结构及其生长机制(英文)

利用包括磁控溅射和热氧化的两步法在Si(111)衬底上制备了Sn掺杂ZnO纳米针.首先用磁控溅射法在Si(111)衬底上制备Sn:Zn薄膜,然后在650℃的Ar气氛中对薄膜进行热氧化,制备出Sn掺杂ZnO纳米针.样品的结构、成分和光学性质采用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、高分辨透射电子显微镜(HRTEM)、能量散射X射线(EDX)谱和光致发光(PL)光谱等技术手段进行分析.结果表明,制备的样品为具有六方纤锌矿结构的单晶Sn掺杂ZnO纳米针,Sn掺杂量为2.5%(x,原子比),底部和头部直径分别为200-500 nm和40 nm,长度为1-3μm,结晶质量较高.室温光致发光光谱显示紫外发光峰比纯ZnO的发光峰稍有蓝移,这可归因于能谱分析中探测到的Sn的影响.基于本实验的实际条件,简单探讨了Sn掺杂ZnO纳米针的生长机制.     

Polyvinylpyrrolidone-assisted growth and optical properties of ZnO hexagonal bilayer disk-like microstructures

ZnO hexagonal bilayer disk-like microstructures are successfully prepared assisted with polyvinylpyrrolidone (PVP), and the photoluminescence (PL) spectrum of as-prepared ZnO samples showed a very strong ultraviolet (UV) emission at the UV region.     

Ion-exchange synthesis and improved photovoltaic performance of CdS/Ag2S heterostructures for inorganic-organic hybrid solar cells

A facile ultrasound-assisted ion exchange route was developed for the synthesis of CdS/Ag₂S heterojunctions by ion exchange between the nanostructured CdS film and [Ag(NH₃)₂]⁺ under ultrasonication. The CdS/Ag₂S heterojunction film was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis DRS spectroscopy, photoelectrochemical measurements, and the transient photovoltage (TPV) technique. CdSAg₂S heterojunctions exhibit a dense morphology, enhanced visible light absorption and stronger photocurrent response than the pure CdS films. Poly(3-hexylthiophene) (P3HT) was then spin coated into the CdS/Ag₂S framework. Hybrid solar cells constructed with FTO/CdS/Ag₂S/P3HT/Au display relatively higher power conversion efficiency than FTO/CdS/P3HT/Au.     

Calcination temperature-dependent morphology of photocatalytic ZnO nanoparticles prepared by an electrochemical–thermal method

ZnO nanoparticles (NPs) with tunable morphologies were synthesized by a hybrid electrochemical–thermal method at different calcination temperatures without the use of any surfactant or template. The NPs were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction, dynamic light scattering, thermogravimetry–differential thermal analysis, scanning electron microscope and N₂ gas adsorption–desorption studies. The FT-IR spectra of ZnO NPs showed a band at 450 cm^?1, a characteristic of ZnO, which remained fairly unchanged at calcination temperatures even above 300 °C, indicating complete conversion of the precursor to ZnO. The products were thermally stable above 300 °C. The ZnO NPs were present in a hexagonal wurtzite phase and the crystallinity of ZnO increased with an increasing calcination temperature. The ZnO NPs calcined at lower temperature were mesoporous in nature. The surface areas of ZnO NPs calcined at 300 and 400 °C were 51.10 and 40.60 m² g^?1, respectively, which are significantly larger than commercial ZnO nanopowder. Surface diffusion has been found to be the key mechanism of sintering during heating from 300 to 700 °C with the activation energy of sintering as 8.33 kJ mol^?1. The photocatalytic activity of ZnO NPs calcined at different temperatures evaluated by photocatalytic degradation of methylene blue under sunlight showed strong dependence on the surface area of ZnO NPs. The ZnO NPs with high surface area showed enhanced photocatalytic activity.     

Effect of the cadmium ion source on the structural and optical properties of chemical bath deposited CdS thin films

The chemical bath deposition (CBD) technique has been successfully used to deposit cadmium sulphide from cadmium chloride and cadmium acetate as the cadmium ion source and thiourea as the sulphur source on both glass microscope slide and indium tin oxide coated glass substrates. Various properties of the films such as surface morphology, crystallinity, optical properties and resistivitiy have been investigated. XRD patterns reveal that the CdS films deposited from cadmium chloride have an hexagonal structure. Their preferential orientation changes from (002) to (100) with the thermal annealing. Films deposited from cadmium acetate are amorphous but improve their crystallinity with annealing. SEM analysis shows that the grains of the as deposited films are randomly shaped and appear to be bigger in the case of the CdS prepared from cadmium chloride. The optical transmission of the layers are in the 70–80 % range for wavelength above the band gap absorption which makes them more appropriate as window material in heterojunction solar cells.     

Solvent dependent growth of fibrous and non-fibrous nanocrystalline thin films of ZnO

Zinc oxide thin films were prepared from three different solvents using the sol–gel technique. Zinc acetate was used as the source of Zn, and the solvents ethanol, 2-methoxy ethanol and ethylene glycol were used to prepare the sols. ZnO thin films were deposited on glass microslides by pre-heating dip coated sol layers, following which they were finally annealed at 450 °C for half an hour. The films were characterized using structural, morphological and optical techniques. XRD studies show that the films grown from all the three solvents were single phase, highly oriented (along the c axis) ZnO having the wurzite structure. Optical transmission and photoluminescence spectra confirm the good quality of the ZnO films. SEM and AFM images show that the surfaces of the ZnO films, obtained using the first two (more volatile) solvents, consist of striations or ridges of height around 100–400 nm and are made up of nanoparticles 20–40 nm in size. The surfaces of the films produced from the less volatile third solvent are however smooth and devoid of striations although they are also covered with nanoparticles.     

CdS量子点敏化ZnO纳米棒阵列电极的制备和光电化学性能

采用连续式离子层吸附与反应法制备了CdS量子点敏化的ZnO纳米棒电极.应用扫描电子显微镜(SEM)、X射线衍射(XRD)和透射电子显微镜(TEM)对CdS量子点/ZnO纳米棒电极的形貌、晶型和颗粒尺寸进行了分析和表征;采用光电流-电位曲线和光电流谱研究了不同CdS循环沉积次数及不同沉积浓度对复合电极的光电性能影响.结果表明,前驱体浓度都为0.1mol·L-1且沉积15次敏化后的ZnO纳米棒阵列电极光电性能最好.与单纯的ZnO纳米棒阵列电极和单纯的CdS量子点电极相比,其光电转换效率显著提高,单色光光子-电流转换效率(IPCE)在380nm处达到76%.这是因为CdS量子点可以拓宽光的吸收到可见光区,并且在所形成的界面上光生载流子更容易分离.荧光光谱实验进一步说明了光电增强的原因是,两者间形成的界面中表面态大大减少,有利于减少光生电子和空穴的复合.     

Highly efficient photoelectrochemical hydrogen generation using a ZnO nanowire array and a CdSe/CdS co-sensitizer

Highly efficient photoelectrochemical (PEC) hydrogen generation was achieved by fabricating CdSe deposited ZnO/CdS core/shell nanowire (NW) array photoanodes by a facile three-step solution-based method. Well-defined electrical pathways in 1-dimensional (1D) NW structures allowed efficient charge carrier collection, and CdSe/CdS co-sensitization enabled utilization of the visible region in the solar spectrum. PEC devices using CdSe/CdS/ZnO NW arrays showed improved absorption spectra, and they demonstrated a remarkable enhancement in PEC performance. Our proposed structure is a promising candidate photoanode for solar energy-to-hydrogen conversion devices.     

Electrochemical fabrication and characterization of p-CuSCN/n-ZnO heterojunction devices

p-CuSCN/n-ZnO heterojunction devices were prepared by depositing CuSCN electrochemically over a ZnO film previously deposited. The compact and smooth surface films of n-ZnO on FTO substrate were deposited electrochemically from a nonaqueous bath. The CuSCN films were characterized by cyclic voltammetry, chronoamperometry, SEM, energy-dispersive X-ray spectroscopy, and XRD measurements. The pure crystalline films of CuSCN with intrinsic trigonal pyramidal morphology over the ZnO films were obtained electrochemically by fixing the SCN/Cu ratio in the electrolytic bath 1.5:1 at 60 °C with ?0.4 V deposition potential. Photocurrent measurements showed the increase of intrinsic surface states or defects in ZnO/CuSCN interface. The I–V characteristic of p-CuSCN/n-ZnO heterojunctions shows good rectification behavior with a rectification ratio of 250 at ±2 V. The value of 2.81 of the ideality factor calculated by fitting the semilogarithmic I–V data with the ideal diode equation revealed the better electrical contact between the smooth ZnO and CuSCN films than that of ZnO nano-rods and CuSCN crystallites.     

Aptamer based photoelectrochemical determination of tetracycline using a spindle-like ZnO-CdS@Au nanocomposite

The authors have synthesized spindle-like ZnO nanorods closely anchored to CdS nanoparticles (NPs) placed on gold NPs (ZnO-CdS@Au). It is shown that the ZnO-CdS@Au nanocomposite can serve as a photoactive material for use in photoelectrochemical (PEC) detection by efficiently absorbing light and then promoting electron transfer. A visible light-driven PEC detection platform for tetracycline (TET) was fabricated by placing the nanocomposite on an ITO and immobilizing the TET-binding aptamer as biorecognition element. PEC can be quantified by applying a bias potential of +?0.4 V (vs. SCE) and visible light irradiation. The aptamer on the electrode specifically captures the TET present in the solution to produce a restored photocurrent signal through the reaction between the captured TET and the photogenerated holes. The electrode has a linear response in the 50 to 200 nM TET concentration range, with a 4.5 nM detection limit (at an S/N ratio of 3). In our perception, this novel PEC detection strategy based on ZnO-CdS@Au nanocomposite demonstrated an ultrasensitive method for TET detection with high selectivity and good stability.

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Graphical abstract Gold nanoparticles and CdS nanoparticles were deposited on the spindle-like ZnO nanorod surface (ZnO-CdS@Au). Photoelectrochemical detection of tetracycline (TET) was realized with high selectivity and good stability utilizing ZnO-CdS@Au as transducer and TET-binding aptamer as biorecognition element.

     

Investigation of the structural properties of annealed CdIn2Te4/CdS thin film solar cells produced by the electron-beam evaporation (e-beam) technique

Thin film CdIn₂Te₄/CdS solar cells were deposited onto the ITO-coated glass substrate by electron beam evaporation (e-beam) technique, and the the effect of annealing on their structural properties is studied. The annealing was performed under nitrogen atmosphere for 1 h. The manufactured solar cells were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDAX) analysis. Crystallite size (D), inter-planer distance (d) and lattice constant (a) values were calculated for the thin film solar cell from XRD data. Annealed samples display well defined XRD patterns with three diffraction peaks. We observed increased peak intensity in the annealed films. EDAX analysis showed that only CdIn₂Te₄ is present in absorber layer and CdS is found in the window layer, but no impurity atoms are present the structure. It is observed that surface roughness of the annealed films incresed, according to SEM images. The I–V characteristics show that the current is increased for annealed thin films solar cells.