KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Search Results

Now showing 1 - 10 of 18

Some of the metrics are blocked by your
consent settings
Effect of Mn doping in CdS quantum dot sensitized solar cells grown by SILAR method
(2021-01-01)
Srisomroop, Juthapak
;
Wichaiyo, Napasuda
;
Gaewdang, Thitinai
;
Wongcharoen, Ngamnit
;
Limsuwan, Pichet
The manganese-doped cadmium sulfide (Mn-doped CdS) quantum dots on titanium dioxide nanoparticles was fabricated using the successive ionic layer absorption and reaction (SILAR) method. The quantum dots were applied to photovoltaic cells. The mixing percentage of manganese in cadmium sulfide precursors was in the range of 1-20 mol%. The study of transport mechanisms and photovoltaic properties of the Mn-doping into CdS QD were investigated using a solar simulator (AM 1.5 G) and current-voltage (J-V) measurements in the dark and under illumination conditions (100 mW/cm2) at room temperature. The photovoltaic performance results indicate that Mn-doped in CdS ratio of 15 mol% exhibits the photovoltaic performance maximum convention efficiency (PCE) is 0.33%. The X-ray diffraction (XRD) patterns of Mn/CdS photoanodes show the nanoparticle average grain size in the range of 4-5 nm, which the formation of the nanoparticles was confirmed by scanning electron microscopy (SEM). The energy dispersion spectroscopy (EDS) shows that Mn is doped into the lattice of CdS QDs. The optical property of the quantum dots was investigated by UV-VIS absorption spectroscopy. The optical band gap was obtained and found to be 2.19 eV from Tauc's plot technique.
Some of the metrics are blocked by your
consent settings
Processing and characterization of amorphous copper oxide thin films prepared by reactive magnetron sputtering
(2018-01-01)
Gaewdang, Thitinai
;
Wongcharoen, Ngamnit
In this paper, copper oxide (CuO<inf>x</inf>) thin films with amorphous phase were prepared on glass substrates by reactive dc magnetron sputtering. The influence of the flow rate of O<inf>2</inf> on the structural, optical and electrical properties of the as-deposited films was systematically studied. XRD revealed that the as-deposited films remained amorphous in the whole range of adjusted oxygen flow rate. Surface morphology and nanoparticle size of the films were observed by AFM. Electrical resistivity and Hall effect measurements were performed on the films with van der Pauw configuration. The positive sign of the Hall coefficient confirmed the p-type conductivity in all studied films. From temperature-dependent electrical conductivity of the films prepared at R(O<inf>2</inf>) of 1.5 sccm, it was show that three types of behavior can be expected, nearest-neighbor hopping at high temperature range (200-300 K), the Mott variable range hopping at low temperature (110-190 K) and Efros-Shklovskii variable range hopping at very low temperature (65-100 K). Some important parameters corresponding to Mott-VRH and ES-VRH like density of localized states near the Fermi level (N(E<inf>F</inf>)), localization length (ξ), degree of disorder(T<inf>0</inf>), hopping distance (R) and hopping energy (W) were determined. These parameters would be helpful for optimizing the performance of photovoltaic applications.
Some of the metrics are blocked by your
consent settings
Electrical properties of nanostructure n-ZnSe/p-Si(100) heterojunction thin film diode
(2018-01-01)
Wongcharoen, Ngamnit
;
Gaewdang, Thitinai
The ZnSe/Si heterojunction is of specific interest since this structure provides effective solar cell and enables the integration of wide bandgap device in silicon circuits. It is known that the quality of the diode and the current transport mechanisms across the heterojunction may be greatly influenced by the quality of the interface and depends on the crystallinity of the film layer. In this work, n-ZnSe/p-Si(100) heterojunction was fabricated by thermal evaporating ZnSe thin films on p-Si (100) substrates. The current-voltage characteristics of n-ZnSe/p-Si(100) heterojunction were investigated in temperature range 20-300 K. Some important parameters such as barrier height, ideality factor and series resistance values evaluated by using thermionic emission (TE) theory and Cheung's method at room temperature are n = 2.910, øB<inf>0</inf> = 0.832 eV and 8.59×103 Ω, respectively. The temperature dependence of the saturation current and ideality factor are well described by tunneling enhanced recombination at junction interface with activation energy and characteristic energy values about 1.293 eV and E<inf>00</inf> = 95 meV, respectively. The carrier concentration of ZnSe thin films about 3.16×1013 cm-3 was deduced from the C-V measurements at room temperature. Admittance spectroscopy was employed for analysis of the defect energy levels situated in depletion region. The results showed that there was a single trap level whose position in the band gap was close to 0.04 eV above valence band. The results of this work may be useful for application such as heterojunction solar cells.
Some of the metrics are blocked by your
consent settings
Structural, optical and photoconductive properties of thermally evaporated CdSxTe1-x thin films
(2017-10-01)
Gaewdang, Thitinai
;
Wongcharoen, Ngamnit
The formation of a CdS<inf>x</inf>Te<inf>1-x</inf> layer by the interdiffusion of S into the CdTe and of Te into CdS films occurs during the fabrication of CdS/CdTe thin film solar cells. The CdS<inf>x</inf>Te<inf>1-x</inf> layer is thought to be important because the real electrical junction is located in this interdiffused CdS<inf>x</inf>Te<inf>1-x</inf> region. Thus, it is important to have a full understanding of the physical properties of CdS<inf>x</inf>Te<inf>1-x</inf> alloy thin films. In this study, CdS<inf>x</inf>Te<inf>1-x</inf> thin films with composition 0 ≤ x ≤ 1 were prepared by thermal evaporation method on glass substrate using powder of pure CdS and CdTe compounds pressed in pellet form as the source in a vacuum of 5.5 10-5 mbar. X-ray diffraction (XRD) revealed that the films exhibited a cubic zincblende structure with the preferred orientation of (111) plane when x < 0.2. However, when x ≥ 0.8, they had a hexagonal wurtzite structure with the preferred orientation of (002) plane. For the composition 0.2 ≤ x ≤ 0.6, the cubic and hexagonal phases coexisted in the system and the films became less preferentially oriented. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to study the morphological features of the samples. The transmission spectra of the films were studied using a double beam spectrophotometer in the wavelength range of 300-900 nm. Optical band gap value of the films was determined from the transmittance spectra. The variation of band gap (E<inf>g</inf>) with composition (x) of the films was in good agreement with the quadratic form, giving a bowing parameter of (b) =1.85 eV. From the transient photoconductivity measurements, persistent photoconductivity (PPC) behavior was observed. The decay current data fit better with multiple exponential functions, resulting in five slow decay times. The longest carrier lifetime of approximately 6,000 s was observed in the films with x = 0.8. Density of trap states corresponding to decay time was also evaluated from the decay current data.
Some of the metrics are blocked by your
consent settings
Tin sulphide prepared by sulphurisation process using metallic tin film precursor obtained from dc magnetron sputtering method
(2017-06-27)
Wongcharoen, Ngamnit
;
Gaewdang, Thitinai
Thin films of tin sulphide were prepared by sulphurisation process of metallic Sn precursor at temperature of 300-500°C in excess ambient of sulphur using a graphite box in N<inf>2</inf> atmosphere. Sulphurisation temperature at 300°C, the films were formed in SnS phase with orthorhombic structure. In contrast, the films were formed in SnS<inf>2</inf> phase with hexagonal structure when sulphurisation temperature higher than 300°C. From absorption spectra, direct band gap increased from 1.70 to 2.45 eV with increasing sulphurisation temperature. From the transient photoconductivity measurements, persistent photoconductivity behavior was observed in the films sulphurised at 300 and 350°C. The decay current data are better fitted with multiple exponential function resulting in the several slow decay times. Density of trap states corresponding to its decay time was also evaluated from the decay current data.
Some of the metrics are blocked by your
consent settings
Influence of oxygen flow rate on structural, optical and electrical properties of copper oxide thin films prepared by reactive magnetron sputtering
(2017-06-27)
Gaewdang, Thitinai
;
Wongcharoen, Ngamnit
In this research, copper oxide thin films were prepared by reactive dc magnetron sputtering method on glass substrates with oxygen flow rate in the range of 1-10 sccm. From XRD patterns, formation of Cu<inf>2</inf>O cubic structure or CuO monoclinic structure was controlled by adjusting oxygen flow rate. Nanocrystallite size of the as-grown films was observed by AFM. From transmittance spectra, direct energy gap varied between 1.97 and 2.55 eV. Electrical conductivity and Hall effect measurements were performed on the films with van der Pauw configuration. The positive sign of the Hall coefficient confirmed the p-type conductivity in all studied films. Important electrical parameters of films as a function of oxygen flow rate were observed. With low resistivity and high mobility values, the films prepared at oxygen flow rate of 8 sccm are identified as suitable candidates for fabrication as absorber layer in solar cell devices.
Some of the metrics are blocked by your
consent settings
Preparation of CuO thin films by thermally oxidized metallic Cu films for CdS/CuO heterojunction diode
(2017-01-01)
Wongcharoen, Ngamnit
;
Gaewdang, Thitinai
Copper thin films were deposited on glass substrates using thermal evaporation in vacuum and then thermally oxidized in air at temperatures of 100-500°C. XRD patterns showed the formation of a fine grain Cu<inf>2</inf>O phase at 300°C and a CuO phase at 400°C, respectively. Crystallinity and grain size improved with increasing oxidation temperature. The energy gap of the samples evaluated from absorption measurements was 2.10-2.23 eV. Important electrical parameters of the CuO thin films obtained from oxidizing at 500°C were resistivity of 8.53x103 Ω•cm, carrier concentration of 7.60x1013 cm-3, and mobility of 6.22 cm2/V•s. A prototype of a CdS/CuO thin-film heterojunction diode was successfully prepared by thermal evaporation of CdS thin films on CuO thin-film substrate in a vacuum. The obtained device exhibited a good rectifying behavior from I-V characteristics. Junction parameters calculated using I-V data were barrier height of 5.190 eV, ideality factor of 0.520, and series resistance of 3.87 O. Impedance spectroscopy of the device was investigated at temperatures of 25-60°C. The real and imaginary parts of the complex impedance changed with the temperature and frequency. The experimental results suggested that the device was a good candidate for photovoltaic devices with low thermal budget and low product cost.
Some of the metrics are blocked by your
consent settings
Influence of annealing temperature on the properties of SnS thin films prepared by vacuum thermal evaporation
(2017-01-01)
Wongcharoen, Ngamnit
;
Gaewdang, Thitinai
SnS thin films were deposited by thermal evaporation in vacuum on glass slide substrate. The as-deposited films were thermally annealed in a controlled N<inf>2</inf> atmosphere with annealing temperature in the range 100-500°C for 30 min. XRD, AFM, UV-VIS transmittance, FTIR and Hall effect measurements were used for characterization the as-deposited and annealed films. Based on the XRD patterns, the as-deposited and annealed films were indentified as the orthrombic structure. The band gap was found to increase from 1.15 to 1.42 eV when the annealing temperature increased from 100 to 500°C. The lowest resistivity and highest carrier concentration values were observed to be 12.95 Ω. cm and 1.98×1016cm-3on the films annealed at 100 and 200°C, respectively.
Some of the metrics are blocked by your
consent settings
Physical properties of CdSxTe1-x thin films prepared by close spaced sublimation method
(2017-01-01)
Gaewdang, Thitinai
;
Wongcharoen, Ngamnit
CdS<inf>x</inf>Te<inf>1-x</inf>(0 ≤ x ≤ 1) thin films were prepared on clear quartz glass substrate by close spaced sublimation method using stoichiometric mixed powders of pure CdS and CdTe compounds. Crystal structure of CdS<inf>x</inf>Te<inf>1-x</inf>thin films was cubic structure with a preferential orientation of (111) plane when the S mole ratio less than 0.2. However, For the composition 0.2 ≤ x ≤ 0.8, the cubic and the hexagonal phases were found to coexist in the system and the films became less preferentially oriented whereas CdS thin films formed in the hexagonal phase with a preferential orientation of (002) plane. SEM micrographs showed the grain size decreased when the S content increased. As the S content increased, the energy gap value of CdS<inf>x</inf>Te<inf>1-x</inf>thin films varied from 1.48 eV (for CdTe) to 2.25 eV (for CdS). Dark electrical sheet resistance of CdS<inf>x</inf>Te<inf>1-x</inf>thin films decreased as a function of S content to minimum value about 2.24×107Ω/sq for x=0.8 and then slightly increased to 4.13×107Ω/sq for x=1.0. From the transient photoconductivity measurements, the highest photosensitivity value about 60.0 was obtained for the films with x = 0.8.
Some of the metrics are blocked by your
consent settings
Influence of Na doping on the thermoelectric properties of CuAlO2 delafossite
(2014-01-01)
Wongcharoen, Ngamnit
;
Gaewdang, Thitinai
The polycrystalline Na-doped CuAlO<inf>2</inf> ceramics were obtained by solid state reaction method. The mixture of high purity grade of CuO, Al<inf>2</inf>O<inf>3</inf> and NaNO<inf>3</inf>·6H<inf>2</inf>O powders was ground and then pressed by using uniaxial pressure. The obtained pellet was sintered in air at 1,423 K for 24 h. XRD patterns showed the crystal structure of the as-sintered Cu<inf>1-x</inf>Na<inf>x</inf>AlO<inf>2</inf> (0≤x≤0.05) belonging to rhombohedral, space group R3m along with the CuO and CuAl<inf>2</inf>O<inf>4</inf> phases. The minimum resistivity value around 4.48x102 Ω ·cm and maximum hole concentration around 2.04x1016 cm-3 were observed for x=0.03 at room temperature. The properties of Seebeck coefficient and electrical resistivity were measured in the high temperature ranging 300 to 700 K. The results of electrical resistivity, Seebeck coefficient and power factor values decrease with increasing Na content. The calculated activation energy of conductivity (in the range of 160-250 meV) is larger than that of thermopower (in the range of 26-83 meV) which suggests that the conduction mechanism may be determined as a small polaron hopping type. © (2014) Trans Tech Publications, Switzerland.

KMITL

Browse

Filters

Settings

Sort By

Results per page

Search Results