S. Yaghmour - Academia.edu (original) (raw)
Papers by S. Yaghmour
The European Physical Journal Applied Physics
ABSTRACT
International Journal of Nanomanufacturing, 2009
Solar Energy Materials and Solar Cells, 2013
ABSTRACT This study demonstrates the feasibility of improving the performance of a quantum dot (Q... more ABSTRACT This study demonstrates the feasibility of improving the performance of a quantum dot (QD) intermediate band solar cell (SC) by capping an InGaAs layer on the InAs QDs and inserting GaAs spacer layers. For comparison, a GaAs reference SC of the same p-i-n structure but without InAs QDs is grown. The two devices were grown by solid source molecular beam epitaxy (SS-MBE) on epiready (001) n+-GaAs substrates and the InAs QDs structure is highly stacked and well-aligned. The two SCs were investigated by sepectroscopic ellipsometry (SE), in the photon energy range of 1–6 eV, photoluminescence (PL) and photo-absorption measurements. The two major spectral features observed in the dielectric function spectra of the InAs QDs SC at ∼3 eV and ∼4.5 eV are attributed to the E1 and E2 critical point structures of GaAs and InAs, respectively. The PL spectrum of the InAs QDs in the GaAs matrix is higher and presents an asymmetric shape, which indicated the growth of a high-quality multistacked InAs QDs structure and the contribution of larger and relatively smaller QDs to PL spectrum. The electrical conversion at the infrared range of λ=850–1300 nm for the InAs QDs SC is demonstrated by photocurrent spectra. The enhanced absorption performance (up to 1280 nm) of the QDs SC was attributed to the optical absorption from InAs QDs, wetting layer and InGaAs layer of the InAs/InGaAs/GaAs QD heterostructure.
Physica B: Condensed Matter, 2009
The dc electrical conductivity of as evaporated thin films of Se 75 S 25Àx Ag x , grown by vacuum... more The dc electrical conductivity of as evaporated thin films of Se 75 S 25Àx Ag x , grown by vacuum evaporation technique is measured as a function of temperature (294-383 K). It is observed that the dc conductivity decreases at all the temperatures with the increase of silver content in the binary system. The experimental data suggests that the conduction is due to thermally assisted tunneling of the carriers in the localized states near the band edges. The extracted value of activation energy is found to increase on incorporation of silver contents in the Se-S system. Compositional dependence of the optical properties of as deposited Se 75 S 25Àx Ag x thin films of thickness 300 nm have also been studied in the spectral range from 400 to 1000 nm. It has been found that the optical band gap increases on incorporation of silver contents in Se-S system. The values of absorption coefficient (a) and extinction coefficient (k) increases with increasing photon energy and silver concentration. The results are interpreted in terms of the change in concentration of localized states due to the shift in Fermi level.
Optical Materials, 2012
ABSTRACT
Materials Letters, 2010
The present work deals with the structural and optical studies of Se88Te12 chalcogenide nanoparti... more The present work deals with the structural and optical studies of Se88Te12 chalcogenide nanoparticles prepared by ball milling. Polycrystalline Se88Te12 chalcogenide prepared by melt quenching was used as a starting material. The ball milling was performed in a Laboratory 8000M-Mixer/Mill (SPEX) mill using hardened steel balls and a vial with a ball-to-powder weight ratio of 10:1. After various times of
Journal of Materials Science Letters, 1988
The reflectance R(~.,) and transmittance ~,k) of an absorbing film of thickness d on a non-absorb... more The reflectance R(~.,) and transmittance ~,k) of an absorbing film of thickness d on a non-absorbing substrate at normal incidence are expressed by Murmann's exact equations [6]. Many authors have applied different methods for determining n and k [7-12]. The most recent methods consist of computerized algorithms intended to solve these complex equations. Several modifications have been made for speeding
Journal of Luminescence, 2013
ABSTRACT
Journal of Electroceramics, 2013
... V Pamukchieva 1, A Szekeres 1,4, E Svab 2, M Fabian 2, Z Revay 3 and L Szentmiklosi 3 1 Georg... more ... V Pamukchieva 1, A Szekeres 1,4, E Svab 2, M Fabian 2, Z Revay 3 and L Szentmiklosi 3 1 Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784 Sofia, Bulgaria 2 Research Institute for Solid State Physics and Optics ...
Journal of Crystal Growth, 2011
Metastable cubic CdSe nanocrystals have been synthesized via solution growth technique along the ... more Metastable cubic CdSe nanocrystals have been synthesized via solution growth technique along the temperature range 55–95°C. The as-synthesized nanocrystals have been characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX). The results indicated that metastable cubic CdSe with the lattice constant a=0.609nm is formed. This cubic structure was found preserved at all temperatures growth. HRTEM measurement confirmed the good crystallinity cubic phase of the CdSe NCs with lattice constant a=0.61nm. The EDX measurement indicated the presence of Cd and Se only with atomic ratio of Cd Se is 0.56:0.44. The optical absorption as a function of the wavelength for the prepared CdSe nanocrystals at different temperatures is investigated. The results indicated the formation of CdSe nanocrystals and their size corresponding to the regime of spatial exciton confinement. The photoluminescence emission intensity for as-synthesized CdSe nanocrystals at different reaction temperatures depicted that at low temperature (55°C) the emission peak intensity of the CdSe QDs was much larger than the absorption edge, indicating the presence of surface trap-state emissions. These surface crystal defects reduced with the increase in the reaction temperature.
Journal of Alloys and Compounds, 2009
The kinetics of crystallization in Se 75 S 25−x Cd x (x = 0, 2, 4, 6 and 8) chalcogenide glasses ... more The kinetics of crystallization in Se 75 S 25−x Cd x (x = 0, 2, 4, 6 and 8) chalcogenide glasses are studied by nonisothermal methods using differential scanning calorimetery at different heating rates of 5, 10, 15 and 20 K/min. The growth kinetics has been investigated using Kissinger, Matusita and Ozawa models. The values of glass transition temperature (T g ), and crystallization temperatures (T c ) are found to be composition and heating rate dependence. From the heating rate dependence of T g and T c , the activation energy for structural relaxation ( E t ), the activation energy of crystallization ( E c ), crystallization enthalpy ( H c ) and the order parameter (n) are calculated. It was observed that the glass transition temperature and crystallization temperatures both increase with increasing heating rates. It was observed that Se 75 S 25 has a minimum value of activation energy of structural relaxation, which indicates that this particular glass has a larger probability to jump to a state of lower configurational energy and higher stability in the glassy region. On the basis of the obtained experimental data the temperature difference (T c − T g ) and the enthalpy released are found to be minimum and maximum, respectively for Se 75 S 21 Cd 4 glass, which indicates that this glass is the least stable glass in the composition range of investigation.
Journal of Alloys and Compounds, 2009
The structural properties of both powder and thermally evaporated pyronine G(Y) thin films have b... more The structural properties of both powder and thermally evaporated pyronine G(Y) thin films have been investigated, using X-ray diffraction technique as well as scanning electron microscope and Fourier transformation infrared FTIR. The powder diffraction pattern has been indexed for the first time. The spectral and the optical parameters have been investigated by using the spectrophotometric measurements of both transmittance and reflectance at normal incidence of light in the wavelength range 200-2500 nm. All the optical investigations have been carried out for the as deposited, annealed (at 393 K/2 h under vacuum) and ␥-irradiated does (by total dose 150 kGy) thin films. Some of the important spectral parameters, namely molar extinction coefficient, oscillator strength and electric dipole strength of the principle optical transitions have been evaluated. The fundamental and the onset indirect energy gaps have been also estimated. The refractive index as a function of wavelength has showed an anomalous dispersion in the absorption region as well as normal dispersion in the transparent region. From analysis of the dispersion curves in the non-absorbing region, the dielectric constants and the dispersion parameters have been obtained. The temperature dependence of the electrical resistivity gives two activation energies related to the extrinsic and intrinsic conduction that depend on the temperature range.
The European Physical Journal Applied Physics, 2013
ABSTRACT Aerogel nanoparticles prepared with various Al concentrations were used as a target for ... more ABSTRACT Aerogel nanoparticles prepared with various Al concentrations were used as a target for the deposition of (V,Al) co-doped ZnO films by rf-magnetron sputtering on glass substrates. The influence of Al content on the structural and the optical properties of the Zn(V,Al)O films was investigated by X-ray diffraction and spectroscopic ellipsometry (SE). It is found that all films exhibit one high intensity (0 0 2) peak, indicating that they have c-axis preferred orientation due to self-texturing mechanism. SE measurements, used to determine the complex pseudo dielectric functions, were carried out at room temperature in the 1-6 eV photon energy region. The excitonic edge of the fundamental band gap (E0) transition in the imaginary part of the dielectric function of the Zn(V,Al)O films is observed around 3.5 eV and shows a dependence on the Al content. The E0 absorption edge of the Zn0.9-x V0.1AlxO alloys shows a blueshift from that of pure ZnO, reaching 389 meV for x = 0.02. This blueshift is interpreted by the Burstein-Moss effect. By analyzing the dielectric function, reduced effective mass m* of the Zn0.9-x V0.1AlxO alloy is extracted and shows good agreement with literature values.
Desalination, 2009
a b s t r a c t a r t i c l e i n f o Transient mathematical models are presented for an active s... more a b s t r a c t a r t i c l e i n f o Transient mathematical models are presented for an active single basin solar still (ASS) with and without a sensible storage material under the basin liner of the still. Sand is used as a storage material due to its availability. The flowing water temperature is assumed to vary with time and space coordinates. Analytical expressions are obtained for various temperatures of the still elements as well as for the temperature of sand. The performance of the still with and without storage is investigated by computer simulation using the climatic conditions of Jeddah (lat. 21°42′ N, long. 39°11′ E), Saudi Arabia. Effects of mass flow rate and thickness of the flowing water for different masses of the storage material on the daylight P dl , overnight P on and daily productivity P d and efficiency η d of the still are studied. The dependence of P d and η d on the thickness and thermal conductivity of the basin liner material is also investigated. It is found that P d and η d decrease as the mass of the storage material increases, due to the increased heat capacity of the storage material. Furthermore, P d and η d are found to decrease with increasing thermal conductivity of the basin linear material. Therefore, it is advisable to fabricate basin liners of ASS from cheap insulating materials such as glass and mica with an optimum thickness of 3 mm. On a summer day, a value of P d of 4.005 (kg/m 2 day) with a daily efficiency of 37.8% has been obtained using 10 kg of sand compared to 2.852 (kg/m 2 day) with a daily efficiency of 27% when the still is used without storage. The annual average of daily productivity of the still with storage is found to be 23.8% higher than that when it is used without storage.
Current Applied Physics, 2009
Applied Surface Science, 2009
Applied Surface Science, 2005
The nanocrystalline ZnS films are successfully produced by sulfidation of the as-deposited ZnO fi... more The nanocrystalline ZnS films are successfully produced by sulfidation of the as-deposited ZnO films of various sputtering time in the H 2 S-H 2 -N 2 mixture. At the deposition time 30 min, after 2 h sulfidation at 500 8C, the as-deposited ZnO films can be converted totally to the hexagonal ZnS films with a strongly (0 0 2) preferred orientation. However, the ZnS films converted from the 10-min deposited ZnO films have a poor crystallinity because of the great influence of the substrates on the properties of the films with the very small thickness. The good crystallinity, the high optical transparency of about 80% in the visible region and the band-gap energy of 3.68 eV are obtained for the ZnS films formed by sulfurizing the 30-min deposited ZnO films. In addition, it is found that the ZnS films produced by sulfurizing the as-deposited ZnO films almost have the same good crystallinity as those prepared by sulfurizing the annealed ZnO films, a reason for which is due to the strongly (0 0 2) preferred orientation during the growth of the ZnS films. This indicates that the ZnS films formed by sulfidation of the as-deposited ZnO films are suitable for use in the thin film solar cells.
Applied Energy, 2010
The measured data of global and diffuse solar radiation on a horizontal surface, the number of br... more The measured data of global and diffuse solar radiation on a horizontal surface, the number of bright sunshine hours, mean daily ambient temperature, maximum and minimum ambient temperatures, relative humidity and amount of cloud cover for Jeddah (lat. 21°42 0 37 00 N, long. 39°11 0 12 00 E), Saudi Arabia, during the period (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007) are analyzed. The monthly averages of daily values for these meteorological variables have been calculated. The data are then divided into two sets. The sub-data set I (1996-2004) are employed to develop empirical correlations between the monthly average of daily global solar radiation fraction (H/H 0 ) and the various weather parameters. The sub-data set II (2005II ( -2007 are then used to evaluate the derived correlations. Furthermore, the total solar radiation on horizontal surfaces is separated into the beam and diffuses components. Empirical correlations for estimating the diffuse solar radiation incident on horizontal surfaces have been proposed. The total solar radiation incident on a tilted surface facing south H t with different tilt angles is then calculated using both Liu and Jordan isotropic model and Klucher's anisotropic model. It is inferred that the isotropic model is able to estimate H t more accurate than the anisotropic one. At the optimum tilt angle, the maximum value of H t is obtained as $36 (MJ/m 2 day) during January. Comparisons with 22 years average data of NASA SSE Model showed that the proposed correlations are able to predict the total annual energy on horizontal and tilted surfaces in Jeddah with a reasonable accuracy. It is also found that at Jeddah, the solar energy devices have to be tilted to face south with a tilt angle equals the latitude of the place in order to achieve the best performance all year round.
The European Physical Journal Applied Physics
ABSTRACT
International Journal of Nanomanufacturing, 2009
Solar Energy Materials and Solar Cells, 2013
ABSTRACT This study demonstrates the feasibility of improving the performance of a quantum dot (Q... more ABSTRACT This study demonstrates the feasibility of improving the performance of a quantum dot (QD) intermediate band solar cell (SC) by capping an InGaAs layer on the InAs QDs and inserting GaAs spacer layers. For comparison, a GaAs reference SC of the same p-i-n structure but without InAs QDs is grown. The two devices were grown by solid source molecular beam epitaxy (SS-MBE) on epiready (001) n+-GaAs substrates and the InAs QDs structure is highly stacked and well-aligned. The two SCs were investigated by sepectroscopic ellipsometry (SE), in the photon energy range of 1–6 eV, photoluminescence (PL) and photo-absorption measurements. The two major spectral features observed in the dielectric function spectra of the InAs QDs SC at ∼3 eV and ∼4.5 eV are attributed to the E1 and E2 critical point structures of GaAs and InAs, respectively. The PL spectrum of the InAs QDs in the GaAs matrix is higher and presents an asymmetric shape, which indicated the growth of a high-quality multistacked InAs QDs structure and the contribution of larger and relatively smaller QDs to PL spectrum. The electrical conversion at the infrared range of λ=850–1300 nm for the InAs QDs SC is demonstrated by photocurrent spectra. The enhanced absorption performance (up to 1280 nm) of the QDs SC was attributed to the optical absorption from InAs QDs, wetting layer and InGaAs layer of the InAs/InGaAs/GaAs QD heterostructure.
Physica B: Condensed Matter, 2009
The dc electrical conductivity of as evaporated thin films of Se 75 S 25Àx Ag x , grown by vacuum... more The dc electrical conductivity of as evaporated thin films of Se 75 S 25Àx Ag x , grown by vacuum evaporation technique is measured as a function of temperature (294-383 K). It is observed that the dc conductivity decreases at all the temperatures with the increase of silver content in the binary system. The experimental data suggests that the conduction is due to thermally assisted tunneling of the carriers in the localized states near the band edges. The extracted value of activation energy is found to increase on incorporation of silver contents in the Se-S system. Compositional dependence of the optical properties of as deposited Se 75 S 25Àx Ag x thin films of thickness 300 nm have also been studied in the spectral range from 400 to 1000 nm. It has been found that the optical band gap increases on incorporation of silver contents in Se-S system. The values of absorption coefficient (a) and extinction coefficient (k) increases with increasing photon energy and silver concentration. The results are interpreted in terms of the change in concentration of localized states due to the shift in Fermi level.
Optical Materials, 2012
ABSTRACT
Materials Letters, 2010
The present work deals with the structural and optical studies of Se88Te12 chalcogenide nanoparti... more The present work deals with the structural and optical studies of Se88Te12 chalcogenide nanoparticles prepared by ball milling. Polycrystalline Se88Te12 chalcogenide prepared by melt quenching was used as a starting material. The ball milling was performed in a Laboratory 8000M-Mixer/Mill (SPEX) mill using hardened steel balls and a vial with a ball-to-powder weight ratio of 10:1. After various times of
Journal of Materials Science Letters, 1988
The reflectance R(~.,) and transmittance ~,k) of an absorbing film of thickness d on a non-absorb... more The reflectance R(~.,) and transmittance ~,k) of an absorbing film of thickness d on a non-absorbing substrate at normal incidence are expressed by Murmann's exact equations [6]. Many authors have applied different methods for determining n and k [7-12]. The most recent methods consist of computerized algorithms intended to solve these complex equations. Several modifications have been made for speeding
Journal of Luminescence, 2013
ABSTRACT
Journal of Electroceramics, 2013
... V Pamukchieva 1, A Szekeres 1,4, E Svab 2, M Fabian 2, Z Revay 3 and L Szentmiklosi 3 1 Georg... more ... V Pamukchieva 1, A Szekeres 1,4, E Svab 2, M Fabian 2, Z Revay 3 and L Szentmiklosi 3 1 Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee, 1784 Sofia, Bulgaria 2 Research Institute for Solid State Physics and Optics ...
Journal of Crystal Growth, 2011
Metastable cubic CdSe nanocrystals have been synthesized via solution growth technique along the ... more Metastable cubic CdSe nanocrystals have been synthesized via solution growth technique along the temperature range 55–95°C. The as-synthesized nanocrystals have been characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX). The results indicated that metastable cubic CdSe with the lattice constant a=0.609nm is formed. This cubic structure was found preserved at all temperatures growth. HRTEM measurement confirmed the good crystallinity cubic phase of the CdSe NCs with lattice constant a=0.61nm. The EDX measurement indicated the presence of Cd and Se only with atomic ratio of Cd Se is 0.56:0.44. The optical absorption as a function of the wavelength for the prepared CdSe nanocrystals at different temperatures is investigated. The results indicated the formation of CdSe nanocrystals and their size corresponding to the regime of spatial exciton confinement. The photoluminescence emission intensity for as-synthesized CdSe nanocrystals at different reaction temperatures depicted that at low temperature (55°C) the emission peak intensity of the CdSe QDs was much larger than the absorption edge, indicating the presence of surface trap-state emissions. These surface crystal defects reduced with the increase in the reaction temperature.
Journal of Alloys and Compounds, 2009
The kinetics of crystallization in Se 75 S 25−x Cd x (x = 0, 2, 4, 6 and 8) chalcogenide glasses ... more The kinetics of crystallization in Se 75 S 25−x Cd x (x = 0, 2, 4, 6 and 8) chalcogenide glasses are studied by nonisothermal methods using differential scanning calorimetery at different heating rates of 5, 10, 15 and 20 K/min. The growth kinetics has been investigated using Kissinger, Matusita and Ozawa models. The values of glass transition temperature (T g ), and crystallization temperatures (T c ) are found to be composition and heating rate dependence. From the heating rate dependence of T g and T c , the activation energy for structural relaxation ( E t ), the activation energy of crystallization ( E c ), crystallization enthalpy ( H c ) and the order parameter (n) are calculated. It was observed that the glass transition temperature and crystallization temperatures both increase with increasing heating rates. It was observed that Se 75 S 25 has a minimum value of activation energy of structural relaxation, which indicates that this particular glass has a larger probability to jump to a state of lower configurational energy and higher stability in the glassy region. On the basis of the obtained experimental data the temperature difference (T c − T g ) and the enthalpy released are found to be minimum and maximum, respectively for Se 75 S 21 Cd 4 glass, which indicates that this glass is the least stable glass in the composition range of investigation.
Journal of Alloys and Compounds, 2009
The structural properties of both powder and thermally evaporated pyronine G(Y) thin films have b... more The structural properties of both powder and thermally evaporated pyronine G(Y) thin films have been investigated, using X-ray diffraction technique as well as scanning electron microscope and Fourier transformation infrared FTIR. The powder diffraction pattern has been indexed for the first time. The spectral and the optical parameters have been investigated by using the spectrophotometric measurements of both transmittance and reflectance at normal incidence of light in the wavelength range 200-2500 nm. All the optical investigations have been carried out for the as deposited, annealed (at 393 K/2 h under vacuum) and ␥-irradiated does (by total dose 150 kGy) thin films. Some of the important spectral parameters, namely molar extinction coefficient, oscillator strength and electric dipole strength of the principle optical transitions have been evaluated. The fundamental and the onset indirect energy gaps have been also estimated. The refractive index as a function of wavelength has showed an anomalous dispersion in the absorption region as well as normal dispersion in the transparent region. From analysis of the dispersion curves in the non-absorbing region, the dielectric constants and the dispersion parameters have been obtained. The temperature dependence of the electrical resistivity gives two activation energies related to the extrinsic and intrinsic conduction that depend on the temperature range.
The European Physical Journal Applied Physics, 2013
ABSTRACT Aerogel nanoparticles prepared with various Al concentrations were used as a target for ... more ABSTRACT Aerogel nanoparticles prepared with various Al concentrations were used as a target for the deposition of (V,Al) co-doped ZnO films by rf-magnetron sputtering on glass substrates. The influence of Al content on the structural and the optical properties of the Zn(V,Al)O films was investigated by X-ray diffraction and spectroscopic ellipsometry (SE). It is found that all films exhibit one high intensity (0 0 2) peak, indicating that they have c-axis preferred orientation due to self-texturing mechanism. SE measurements, used to determine the complex pseudo dielectric functions, were carried out at room temperature in the 1-6 eV photon energy region. The excitonic edge of the fundamental band gap (E0) transition in the imaginary part of the dielectric function of the Zn(V,Al)O films is observed around 3.5 eV and shows a dependence on the Al content. The E0 absorption edge of the Zn0.9-x V0.1AlxO alloys shows a blueshift from that of pure ZnO, reaching 389 meV for x = 0.02. This blueshift is interpreted by the Burstein-Moss effect. By analyzing the dielectric function, reduced effective mass m* of the Zn0.9-x V0.1AlxO alloy is extracted and shows good agreement with literature values.
Desalination, 2009
a b s t r a c t a r t i c l e i n f o Transient mathematical models are presented for an active s... more a b s t r a c t a r t i c l e i n f o Transient mathematical models are presented for an active single basin solar still (ASS) with and without a sensible storage material under the basin liner of the still. Sand is used as a storage material due to its availability. The flowing water temperature is assumed to vary with time and space coordinates. Analytical expressions are obtained for various temperatures of the still elements as well as for the temperature of sand. The performance of the still with and without storage is investigated by computer simulation using the climatic conditions of Jeddah (lat. 21°42′ N, long. 39°11′ E), Saudi Arabia. Effects of mass flow rate and thickness of the flowing water for different masses of the storage material on the daylight P dl , overnight P on and daily productivity P d and efficiency η d of the still are studied. The dependence of P d and η d on the thickness and thermal conductivity of the basin liner material is also investigated. It is found that P d and η d decrease as the mass of the storage material increases, due to the increased heat capacity of the storage material. Furthermore, P d and η d are found to decrease with increasing thermal conductivity of the basin linear material. Therefore, it is advisable to fabricate basin liners of ASS from cheap insulating materials such as glass and mica with an optimum thickness of 3 mm. On a summer day, a value of P d of 4.005 (kg/m 2 day) with a daily efficiency of 37.8% has been obtained using 10 kg of sand compared to 2.852 (kg/m 2 day) with a daily efficiency of 27% when the still is used without storage. The annual average of daily productivity of the still with storage is found to be 23.8% higher than that when it is used without storage.
Current Applied Physics, 2009
Applied Surface Science, 2009
Applied Surface Science, 2005
The nanocrystalline ZnS films are successfully produced by sulfidation of the as-deposited ZnO fi... more The nanocrystalline ZnS films are successfully produced by sulfidation of the as-deposited ZnO films of various sputtering time in the H 2 S-H 2 -N 2 mixture. At the deposition time 30 min, after 2 h sulfidation at 500 8C, the as-deposited ZnO films can be converted totally to the hexagonal ZnS films with a strongly (0 0 2) preferred orientation. However, the ZnS films converted from the 10-min deposited ZnO films have a poor crystallinity because of the great influence of the substrates on the properties of the films with the very small thickness. The good crystallinity, the high optical transparency of about 80% in the visible region and the band-gap energy of 3.68 eV are obtained for the ZnS films formed by sulfurizing the 30-min deposited ZnO films. In addition, it is found that the ZnS films produced by sulfurizing the as-deposited ZnO films almost have the same good crystallinity as those prepared by sulfurizing the annealed ZnO films, a reason for which is due to the strongly (0 0 2) preferred orientation during the growth of the ZnS films. This indicates that the ZnS films formed by sulfidation of the as-deposited ZnO films are suitable for use in the thin film solar cells.
Applied Energy, 2010
The measured data of global and diffuse solar radiation on a horizontal surface, the number of br... more The measured data of global and diffuse solar radiation on a horizontal surface, the number of bright sunshine hours, mean daily ambient temperature, maximum and minimum ambient temperatures, relative humidity and amount of cloud cover for Jeddah (lat. 21°42 0 37 00 N, long. 39°11 0 12 00 E), Saudi Arabia, during the period (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007) are analyzed. The monthly averages of daily values for these meteorological variables have been calculated. The data are then divided into two sets. The sub-data set I (1996-2004) are employed to develop empirical correlations between the monthly average of daily global solar radiation fraction (H/H 0 ) and the various weather parameters. The sub-data set II (2005II ( -2007 are then used to evaluate the derived correlations. Furthermore, the total solar radiation on horizontal surfaces is separated into the beam and diffuses components. Empirical correlations for estimating the diffuse solar radiation incident on horizontal surfaces have been proposed. The total solar radiation incident on a tilted surface facing south H t with different tilt angles is then calculated using both Liu and Jordan isotropic model and Klucher's anisotropic model. It is inferred that the isotropic model is able to estimate H t more accurate than the anisotropic one. At the optimum tilt angle, the maximum value of H t is obtained as $36 (MJ/m 2 day) during January. Comparisons with 22 years average data of NASA SSE Model showed that the proposed correlations are able to predict the total annual energy on horizontal and tilted surfaces in Jeddah with a reasonable accuracy. It is also found that at Jeddah, the solar energy devices have to be tilted to face south with a tilt angle equals the latitude of the place in order to achieve the best performance all year round.