ABSTRACT: Aluminum-doped ZnO (AZO) transparent conducting films were deposited on glass substrates with and without intrinsic ZnO (i-ZnO)
buffer layers by a home made and low cost radio-frequency (RF) magnetron sputtering system at room temperature in pure argon
ambient and under a low vacuum level. The films were examined and characterized for electrical, optical, and structural properties
for the application of CIGS solar cells. The influence of sputter power, deposition pressure, film thickness and residual
pressure on electrical and optical properties of layered films of AZO, i-ZnO and AZO/i-ZnO was investigated. The optimization
of coating process parameters (RF power, sputtering pressure, thickness) was carried out. The effects of i-ZnO buffer layer
on AZO films were investigated. By inserting thin i-ZnO layers with a thickness not greater than 125nm under the AZO layers,
both the carrier concentration and Hall mobility were increased. The resistivity of these layered films was lower than that
of single layered AZO films. The related mechanisms and plasma physics were discussed. Copper indium gallium selenide (CIGS)
thin film solar cells were fabricated by incorporating bi-layer ZnO films on CdS/CIGS/Mo/glass substrates. Efficiencies of
the order of 7–8% were achieved for the manufactured CIGS solar cells (4–5cm2 in size) without antireflective films. The results demonstrated that RF sputtered layered AZO/i-ZnO films are suitable for
application in low cost CIGS solar cells as transparent conductive electrodes.
Journal of Materials Science Materials in Electronics 05/2012; 21(10):1005-1013. · 1.08 Impact Factor
ABSTRACT: Double-walled carbon nanotubes (DWCNTs) have been studied for counter-electrode application in dye-sensitized solar cells
(DSCs). Mesoporous TiO2 films are prepared from the commercial TiO2 nanopowders by screen-printing technique on optically
transparent-conducting glasses. A metal-free organic dye (indoline dye D102) is used as a sensitizer. DWCNTs are applied to
substitute for platinum as counter-electrode materials. Morphological and electrochemical properties of the formed counter
electrodes are investigated by scanning electronic microscopy and electrochemical impedance spectroscopy, respectively. The
electronic and ionic processes in platinum and DWCNT-based DSCs are analyzed and discussed. The catalytic activity and DSC
performance of DWCNTs and Pt are compared. A conversion efficiency of 6.07% has been obtained for DWCNT counter-electrode
DSCs. This efficiency is comparable to that of platinum counter-electrode-based devices.
KeywordsDye-sensitized solar cell-Nanocrystallined TiO2-Metal-free organic dye-Counter electrode-Double-walled carbon nanotube (DWCNT)
Journal of Solid State Electrochemistry 04/2012; 14(9):1541-1546. · 2.13 Impact Factor
ABSTRACT: This paper presents further insights and observations of the chemical bath deposition (CBD) of ZnS thin films using an aqueous
medium involving Zn-salt, ammonium sulfate, aqueous ammonia, and thioure. Results on physical and chemical properties of the
grown layers as a function of ammonia concentration are reported. Physical and chemical properties were analyzed using scanning
electron microscopy (SEM), X-ray energy dispersive (EDX), and X-ray diffraction (XRD). Rapid growth of nanostructured ZnO
films on fluorine-doped SnO2 (FTO) glass substrates was developed. ZnO films crystallized in a wurtzite hexagonal structure and with a very small quantity
of Zn(OH)2 and ZnS phases were obtained for the ammonia concentration ranging from 0.75 to 2.0M. Flower-like and columnar nanostrucured
ZnO films were deposited in two ammonia concentration ranges, respectively: one between 0.75 and 1.0M and the other between
1.4 and 2.0M. ZnS films were formed with a high ammonia concentration of 3.0M. The formation mechanisms of ZnO, Zn(OH)2, and ZnS phases were discussed in the CBD process. The developed technique can be used to directly and rapidly grow nanostructured
ZnO film photoanodes. Annealed ZnO nanoflower and columnar nanoparticle films on FTO substrates were used as electrodes to
fabricate the dye sensitized solar cells (DSSCs). The DSSC based on ZnO-nanoflower film showed an energy conversion efficiency
of 0.84%, which is higher compared to that (0.45%) of the cell being constructed using a photoanode of columnar nanoparticle
ZnO film. The results have demonstrated the potential applications of CBD nanostructured ZnO films for photovoltaic cells.
Applied Physics A 04/2012; 95(3):849-855. · 1.63 Impact Factor
ABSTRACT: Graphene nanosheets (GNs) have been investigated as a counter electrode for dye-sensitized solar cells (DSCs). Mesoporous TiO<sub>2</sub> films are prepared from the commercial TiO<sub>2</sub> nano-powders by screen-printing technique on fluorine-doped tin oxide (FTO) slides. GNs are applied to substitute for platinum as counter-electrode materials. GN films are screen printed on FTO glass using a paste based on GNs dispersed in a mixture of terpineol and ethylcellulose. GN counter-electrodes were prepared by annealing the GN films at different temperatures. A metal-free organic dye (indoline dye D102) is used as a sensitizer. Morphological and electrochemical properties of the formed counter-electrodes are investigated by scanning electronic microscopy and electrochemical impedance spectroscopy (EIS), respectively. The electronic and ionic processes in platinum and GNs based DSCs are analysized and discussed. A conversion efficiency of 2.94 % has been obtained for GNs based DSCs. It is found that the quality of the GN counter-electrode and the photovoltaic performance are strongly affected by the annealing temperature of GN materials.
Nanoelectronics Conference (INEC), 2010 3rd International; 02/2010
ABSTRACT: Titanium dioxide nanotubes (TiNTs) were fabricated from commercial P25 TiO2 powders via alkali hydrothermal transformation. Dye-sensitized solar cells (DSCs) were constructed by application of TiNTs and P25 nanoparticles with various weight percentages. The influence of the TiNT concentration on the performance of DSCs was investigated systematically. The electrochemical impedance spectroscopy (EIS) technique was employed to quantify the recombination resistance, electron lifetime and time constant in DSCs both under illumination and in the dark. The DSC based on TiNT/P25 hybrids showed a better photovoltaic performance than the cell purely made of TiO2 nanoparticles. The open-voltage (Voc), fill factor (FF) and efficiency (η) continuously increased with the TiO2 nanotube concentration from 0 to 50 wt%, which was correlated with the suppression of the electron recombination as found out from EIS studies. Respectable photovoltaic performance of ca. 7.41% under the light intensity of 100 mW cm−2 (AM 1.5G) was achieved for DSCs using 90 wt% TiO2 nanotubes incorporated in TiO2 electrodes.
Materials Chemistry and Physics 124(1):179-183. · 2.23 Impact Factor