Papers by Keyword: CdTe

Abstract: The current study investigated the electrical properties of Cadmium Telluride (CdTe)by using the first principle of density functional theory (DFT). The nanocrystals suggested being varied constantly over the network systematically so that the lowest value for energy is obtained, through which stability is obtained and through this exceptionality, the measurements of the properties are in their exact state. The conduction and the valence bandwidths were also studied. The investigations targeted the “highest occupied molecular orbital” (HOMO) [Ionization Potential], and the “lowest unoccupied molecular orbital” (LUMO) [Electron Affinity]. Total and cohesive energies, the atomic iconicity, electron affinity, energy gap (Eg), and the density of states (DOS) for 8, 16, 54, and 64 atoms. The results showed that the shape of the conduction and valence affect the crystal groups significantly, and the energy gap exhibited very close results to their practical counterparts that were previously conducted. When the lattice constant decreases the modulus of bulk and the waves of sound speed increase with the increase of the core atoms number. Subsequently, the applied pressure increases the Plasmon energy and bulk modulus. The key of study is to inspect if using materials in their nanoscale state gives special physical, electronic and optical properties through which devices are manufactured with high efficiency in the solar cell industry. Where the compound becomes a point of a sleeve, and the fluorescent peak shifts across the visible field to the UV field. This was obtained by controlling the size of the compound in 54 and 64, at which the energy gap showed an increase, which would make it more preferred to stimulate the electron from the valence band to the conduction band.

Abstract: New nanocrystals (NCs) were engineered with a core/shell/shell system consisting of CdSe core/ CdTe shell/ CdS shell. The white light generation mechanism was described depending on mixing colors from the illuminated CdSe/CdTe/CdS core/shell/shell nanocrystals. The color mixed in CdSe/CdTe/CdS core/shell/shell NCs system were used to generate extreme white light when illuminated by InGaN/GaN UV LED (λ=360 nm) the core/shell/shell NCs system tuned the chromaticity coordinates to (0.332, 0.340) and increased the intensity of the emitted white light. The synthesis of the CdSe/CdTe/CdS core/shell/shell NCs were confirmed by SEM, AFM, XRD and photoluminescence (PL) experiments due to create of surface states defects information. This enhancement was recognized to the overlap of emission with the photoluminescence (PL) spectrum of CdSe/CdTe/CdS core/shell/shell NCs which indications to a cold white light generation. Current-voltage (I–V) characteristics indicate that the output current is good compared to the few voltages (6 V) used which give acceptable results to get a generation of white light.

Abstract: In this article, simulation results of novel and facilitated heterostructures of the Second Generation (2G) Thin-film Solar Cells (TFSCs): hydrogenated amorphous Silicon (a-Si:H), Cadmium Telluride (CdTe), and Copper Indium Gallium di-Selenide (Cu(In,Ga)Se₂ or CIGS) have been presented to compare their performances. The solar cells have been modeled and analyzed for investigating optimized structure with higher stabilized efficiency. Entire simulations have been accomplished using Analysis of Microelectronic and Photonic Structures – 1 Dimensional (AMPS-1D) device simulator. The thickness of the absorber layer was varied from 50 nm to 1400 nm for a-Si:H and from 50 nm to 3 μm for both CdTe and CIGS cells to realize its impact on cell performance. The utmost efficiency, η of 9.134%, 20.776%, and 23.03% were achieved at AM 1.5 (1000 W/m²) for a-Si:H, CdTe, and CIGS material cells, respectively. Lastly, the operating temperature of the three cells was varied from 280°K to 328°K to realize its effect on the cell PV performances.

Abstract: Cadmium telluride CdTe QDs was prepared by chemical reaction and used to fabricate electroluminescence quantum dot hybrid junction device. QD-LED was fabricated using TPD: PMMA/CdTe/Alq₃ device which synthesized by phase segregation method. The hybrid white light emitting devices consists, of three-layers deposited successively on the ITO glass substrate; the first layer was of Tetra-Phenyl Diaminobiphenyl (TPD) polymer mixed with polymethyl methacrylate (PMMA) polymers, while the second layer was 0.5wt% of the (CdTe) QDs for hybrid device, whereas the third layer was Tris (8-hydroxyquinoline) aluminium (Alq₃). The optical properties of CdTe QDs were considered by UV-Vis. and photoluminescence (PL) spectrometer. The results show that the prepared QDs were nanocrystalline with defects formation. The Eg calculated from PL were 2.25 eV for Cadmium telluride CdTe QDs was prepared by chemical reaction and used to fabricate electroluminescence quantum dot hybrid junction device. QD-LED was fabricated using TPD: PMMA/CdTe/Alq3device which synthesized by phase segregation method. The hybrid white light emitting devices consists, of three-layers deposited successively on the ITO glass substrate; the first layer was of Tetra-Phenyl Diaminobiphenyl (TPD) polymer mixed with polymethyl methacrylate (PMMA) polymers, while the second layer was 0.5wt% of the (CdTe) QDs for hybrid device, whereas the third layer was Tris (8-hydroxyquinoline) aluminium (Alq3). The optical properties of CdTe QDs were measuredby UV-Vis. and photoluminescence (PL) spectrometer. The results show that the prepared QDs were nanocrystalline with defects formation. The Eg calculated from PL were 2.25 eV for CdTe QDs. The generated white light properties with acceptable efficiency using confinement effect that makes the energy gap larger, thus the direction of the light sites are toward the center of white light color. The organic light emitting device (OLED) wasconsidered by room temperature PL and electroluminescence (EL). Current-voltage (I–V) characteristics indicate that the output current is good compared to the few voltage (6 V) used which gives good results to get a generation of white light. The electroluminescence (EL) spectrum of hybrid deviceshows a wide emission band covering the range from 350 - 700 nm. The emissions causing this white luminescence were identified depending on the chromaticity coordinates (CIE 1931) was found (x=0.32, y=0.33). The correlated color temperature (CCT) was found to be about 5886 K. Fabrication of EL-devices from semiconductors material (CdTe QDs) between two layers organic polymer (TPD) and organic molecules (Alq3) were effective in white light generation. The recombination processes and I-V characteristics gives rises to the output current is good compared to the few voltages used which gives good results to become a generation of light.

Abstract: The white light generation mechanism was explained depending on mixing colors from the illuminated CdTe/ZnSe core/shell nanocrystals. The color mixed in CdTe/ZnSe core/shell system were used to generate intense white light when illuminated by InGaN/GaN UV LED (λ=360 nm) the core/shell system tuned the chromaticity coordinates to (0.30, 0.32) and increased the intensity of the emitted white light. This improvement was attributed to the overlap of emission with the photoluminescence (PL) spectrum of CdTe/ZnSe core/shell which leads to a cold white light generation.

Abstract: The effect of Cu substitution for Cd an Te atoms in CdTe crystal were examined by using ab initio calculations. Depending of location of Cu atom in the super cell, band gap changes and metallic behaviour of CdTe has been obtained.

Abstract: The large area CdTe thin film samples were used for chloride annealing. The CuCl₂/NH₄Cl solution was attached on the CdTe surface. After annealing treatment, the CdTe solar cells were prepared. The structure of the thin films and the properties of the CdTe solar cells were tested for studying the effect of the ratio of Cu/Cl, solution concentration and the annealing temperature. At last the performance of CuCl₂/NH₄Cl annealing cells, ZnTe back contact cells and C:Te,Cu back contact cells were compared. Without back contact layers the efficiency of the CdTe solar cells reached 11.13% with chloride annealing.

Abstract: This study reports the cycle chemistries involved in depositing CdTe and PbTe nanofilms. An automated thin-layer flow cell electrodeposition system was used to deposit the films at room temperature. Cyclic voltammetry was used to study the Underpotential Deposition (UPD) of the compounds. The monolayer/cycle deposition rate was also monitored in order to insure that the film is depositing at a uniform rate. The chemical composition of the films was characterized using Energy-Dispersive X-ray Spectroscopy (EDS) on a Scanning Electron Microscope (SEM). The crystallinity of the films was studied using a glancing angle X-ray diffractometer. The bandgaps of the films were calculated using measured optical reflection data.

Abstract: We have developed a new, simple, green and very reproducible aqueous synthesis method for the preparation of different sizes CdTe QDs without the use of any pyrophoric organometallic precursors. Transmission electron microscope image demonstrates the shape, monodispersity, average size and size distribution. Two different sizes CdTe QDs are mixed and standing for three months in aqueous solution. Through UV-Vis absorption spectroscopy and fluorescence spectrum detection, we confirm Ostwald ripening process can also occur in CdTe QDs mixed solution for a long time at room temperature.

Abstract: In this paper，CdTe thin films were successfully grown at higher source temperatures of 650 °C and 700 °C using close-spaced sublimation(CSS) and characterized by energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), scanning electron microscope (SEM), UV-Vis-NIR absorption spectra, respectively. The results indicated that the grain size of CdTe thin film increased from 1 μm to 5 μm with the increase of the source temperature from 650 °C to 700 °C. The direct band gaps of CdTe thin films prepared at different source temperatures of 650 °C and 700 °C were 1.44 and 1.43 eV, respectively.