Activating ZnO nanorod photoanodes in visible light by CdS surface sensitizer (original) (raw)
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Photoelectrochemical properties of CdS sensitized ZnO nanorod arrays: Effect of nanorod length
2012
The vertically aligned ZnO nanorod arrays were achieved from aqueous chemical route on soda lime and transparent conducting oxide coated glass substrates. The length of nanorods was varied from 1.6 lm to 4.5 lm by varying deposition time. The aspect ratio of ZnO nanorod was increased with increasing deposition time. Cadmium sulfide (CdS) nanoparticles have been subjected to self-assemble onto ZnO nanorods (ZNRs) using chemical bath deposition method. The synthesized CdS/ZnO nanorod arrays were characterized for their optical, structural, and morphological properties with UV-visible absorption spectroscopy (UV-Vis), x-ray diffraction, energy-dispersive x-ray analysis, x-ray photoelectron spectroscopy, contact angle measurement, and scanning electron microscopy. The cross-section images of the samples clearly depict different lengths of ZnO nanorods. UV-vis absorption spectrum shows the significant red shifting after covering of the CdS nanoparticles over the ZnO nanorods. The lengths of ZnO nanorod arrays are an effective parameter to improve the photoelectrochemical performance of CdS nanoparticles sensitized ZnO solar cells. We obtain a highest total light-to-electricity power conversion efficiency of 1.2% for relatively larger area (1 cm 2 ) solar cells. V C 2012 American Institute of Physics. [http://dx.
Low temperature aqueous chemical synthesis of CdS sensitized ZnO nanorods
2011
Cadmium sulfide nanoparticles (CNPs) sensitized zinc oxide nanorod arrays (ZNRs) were synthesized in the two step deposition process at relatively low temperature. The vertically aligned ZNRs were grown on the conducting glass substrates (FTO) using aqueous chemical method, followed by the deposition of CNPs at 70°C using chemical bath deposition (CBD) technique. The samples were characterized by optical absorption, X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy (PL). Further, the photoelectrochemical (PEC) performance of ZNRs with and without CNPs sensitization was tested in Na 2 S-NaOH-S and Na 2 SO 4 electrolyte, respectively. When the CNPs are coated on the ZNRs, the optical absorption is enhanced and band edge is shifted towards visible region (525 nm) as compared with ZNRs (375 nm). The sample sensitized with CNPs shows higher photoelectrochemical (PEC) performance with maximum short circuit current of (I sc ) 2.60 mA/cm 2 .
Spectral Dependent Photoelectrochemical Behaviors of CdS Sensitized ZnO Nanorods
Journal of Nanoscience and Nanotechnology, 2016
CdS decorated ZnO nanorods have been grown by a combination of hydrothermal method and successive ion layer absorption and reaction (SILAR) method. Optical absorption and emission properties of ZnO nanorods have been studied after sensitization with CdS nanoparticles. Current– voltage characteristics of ZnO nanorods and CdS sensitized ZnO nanorods have been studied in an electrochemical cell. The spectral dependent photocurrent and photopotential behaviors of ZnO nanorods and CdS sensitized ZnO nanorods have been investigated using monochromatic light of wavelength 300–700 nm. The photopotential recovery time have been estimated for CdS sensitized nanorods and pristine nanorods.
Advances in OptoElectronics, 2011
Thin films of ZnO semiconductor nanorods (ZnO-nr) of 6 μm length and thin ZnO nanoparticulate films (ZnO-np) have been prepared and modified with Q-dots CdS for comparison study. PIA (photoinduced absorption spectroscopy), a multipurpose tool in the study of dye-sensitized solar cells, is used to study a quantum-dot-modified metal-oxide nanostrucutred electrode. Q-dot CdS-sensitized ZnO-nr (1D network) sensitized photoelectrode has demonstrated best performances in both photoelectrical response (IPCE max = 92%) and broadening response into far visible comparing to ZnO-np-based CdS solar cell. Preadsorbing ZnO-nr with ZnO-np does not bring further improvement. Time constant for electron injection into ZnO-nr conduction band was relatively fast decay of 6.5 ms, similar to TiO2-coated CdS, and proves at least a well pore filling of ZnO-nr film by ultrafine CdS particles. Unidirectional electron transfer mechanistic in ZnO-nr has played a major role in these performances.
PEC electrode of ZnO nanorods sensitized by CdS with different size and its photoelectric properties
International Journal of Hydrogen Energy, 2013
The gradient PEC electrodes of ZnO nanorods sensitized by CdS with different size were fabricated via successive ionic layer adsorption and reaction (SILAR) method and applied in photochemical water splitting. The concentrations of reaction solution and SILAR cycles were investigated in the synthetic process and the working mechanism of the gradient PEC electrode was suggested. The results showed that the hydrogen generation efficiency of 4.88% was achieved for the ZnO/CdS gradient PEC electrode constructed by decreasing of the CdS quantum dots size on ZnO nanorods due to the improved absorption and appropriate energy gap structure, which was confirmed by enhanced absorption spectrum. The expected products have potential application in photoelectrochemical water splitting.
Journal of Colloid and Interface Science, 2018
Controlled growth of different sizes of cadmium selenide (CdSe) nanoparticles over well aligned ZnO nanorods have been performed using successive ionic layer adsorption and reaction (SILAR) technique at room temperature (27 o C) in order to form nano heterostructure solar cells. Deposition of compact layer of zinc oxide (ZnO) by SILAR technique on fluorine doped tin oxide (FTO) coated glass substrate followed by growth of vertically aligned ZnO nanorods array using chemical bath deposition (CBD) at low temperature (<100 o C). Different characterization techniques viz. X-ray diffractometer, UV-Vis spectrophotometer, field emission scanning electron microscopy and X-ray photoelectron spectroscopy have been used to know the structural, optical, morphological and compositional properties of synthesized nano heterostructure. The photovoltaic performance of the cells with variation in SILAR cycles for CdSe and with use of different electrolytes have been recorded as J-V characteristics and the maximum conversion efficiency of 0.63% have been attained with ferro/ferri cyanide electrolyte for 12 cycles CdSe coating over 1-D ZnO nanorods.
Array of CdSe QD-Sensitized ZnO Nanorods Serves as Photoanode for Water Splitting
Journal of The Electrochemical Society, 2010
Aqueous chemically grown ZnO nanorods ͑NRs͒ arrays were sensitized by CdSe quantum dots ͑QDs͒ and were investigated as photoanode for photoelectrochemical water splitting under visible light ͑Ͼ420 nm͒ illumination. Significant enhancement of the factors 1.6 and 6 was observed for CdSe ͑QD͒-sensitized nonannealed and annealed samples of ZnO NRs over pristine ZnO NRs arrays, respectively. The highest photocurrent density of 2.48 mA/cm 2 was registered for the annealed CdSe ͑QD͒/ZnO ͑NR͒ arrays films at zero applied voltage and 100 mW/cm 2 ͑AM 1.5 G, Air Mass 1.5 Global͒ power density and their corresponding photocurrent density for pristine ZnO NR array was recorded as 0.41 mA/cm 2 .
Journal of Electroanalytical Chemistry, 2018
The ZnO nanorods electrochemically deposited on FTO substrate were covered with CdSe by means of two different procedures: successive ionic layer adsorption and reaction (SILAR) and electrochemical pulse methods. The electrodeposition was performed in alkaline solution containing Na 2 SeSO 3 and Cd(NTA) − complex. The number of SILAR cycles and charge density involved in electrodeposition of CdSe were adjusted to obtain the same ZnO loading with light-absorbing semiconductor. Photoelectrochemical properties of these two types of FTO/ZnO/CdSe electrodes in aqueous solution containing S 2 − /S n 2 − redox couple are compared. The highest photocurrents and open circuit potential values under illumination were obtained for the samples with CdSe deposited in 10 SILAR cycles and electrodeposited at the charge density of 100 mC cm − 2. A dependence of the CdSe stoichiometry (determined from EDX spectra) and photoactivity of the both types of ZnO/CdSe composites on the synthesis conditions (number of SILAR cycles, precursor concentration, potential and current density) are discussed.
Formation of a CdO layer on CdS/ZnO nanorod arrays to enhance their photoelectrochemical performance
ChemSusChem, 2014
The performance and photocatalytic activity of the well-known CdS/ZnO nanorod array system were improved significantly by the layer-by-layer heterojunction structure fabrication of a transparent conductive oxide (TCO) CdO layer on the CdS/ZnO nanorods. Accordingly, a CdO layer with a thickness of approximately 5-10 nm can be formed that surrounds the CdS/ZnO nanorod arrays after annealing at 500 °C under air. At an external potential of 0.0 V vs. Ag/AgCl, the CdO/CdS/ZnO nanorod array electrodes exhibit an increased incident photon to conversion efficiency, which is significantly higher than that of the CdS/ZnO nanorod array electrodes. The high charge separation between the electrons and holes at the interfaces of the heterojunction structure results from the specific band energy structure of the photoanode materials, and the unique high conductivity of the CdO layer is attributed to the suppression of electron-hole recombination; this suppression enhances the photocurrent density ...
CdSe quantum dots sensitized ZnO nanorods for solar cell application
Materials Letters, 2018
Sol gel dip coating method has been used for preparing ZnO nanorods. ZnO nanorods have been sensitized using CdSe quantum dots by simple chemical method. Uniform coverage of quantum dots on ZnO nanorods is observed. The structural, optical and morphology of the ZnO nanorods, CdSe quantum dots and CdSe quantum dot sensitized ZnO nanorods have been studied. The presence of CdSe quantum dots in ZnO nanorods based film is clearly seen in FESEM and TEM image and the elements Zn, O, Cd and Se present in the film was confirmed by EDAX analysis. FTO/CdSe quantum dot-ZnO nanorods/electrolyte/platinum structure based solar cell has been fabricated and the cell efficiency has been found to be 2.1%.