Papers by Keyword: CdTe

Abstract: The development of CdTe/CdS solar cells on flexible substrates is reviewed in this article. Photovoltaic structures on lightweight and flexible substrates have several advantages over the heavy glass based structures in both terrestrial and space applications. The cells mounted on flexible foil are not fragile, the requirements of the supporting structures are minimum and they can be wrapped onto any suitably oriented or curved structures. The specific power of the solar cells is an important factor in space applications and hence development of photovoltaic devices on light weight substrates is interesting. CdTe is one of the leading candidates for photovoltaic applications due to its optimum band gap for the efficient photo-conversion and robustness for industrial production with a variety of film preparation methods. Flexible solar cells with conversion efficiencies exceeding 11% have been developed on polyimide foils. The development of CdTe devices on metallic substrates is impeded due to the lack of a proper ohmic contact between CdTe and the substrate. The polymer substrate has the advantage that the devices can be prepared in both “superstrate” and “substrate” configurations.

Abstract: Highly fluorescent Cadmium based II-VI CQD’s plays a vital role in third generation photovoltaic’s design. In this paper, a novel approach for rapid synthesis of two different high quality cadmium based CQD’s in aqueous phase was presented and the optical stability and the structural properties of those materials were studied out. In this work Tellurium composed CQD’s along with cadmium were prepared by colloidal route. In the above procedure Thio Glycolic Acid (TGA) as well as Mercapto succinic acids (MSA) was used as the capping agents. All these procedures were carried out in aqueous medium at air atmosphere. The size dependent band gaps of the prepared quantum dots were determined from UV-Vis spectra and compared with the other one. The fluorescent properties of CdTe CQDs were investigated by using fluorescence spectra. The surface and structural morphologies were determined by using HRSEM and X-ray diffraction studies. The formation of CdTe quantum dots and the capping effect of the thiol group were investigated from EDAX and FTIR analysis.

Abstract: After reviewing the development of CdTe solar cells, the merits of superstrate and substrate configuration have been discussed. Then, the material process techniques are investigated according to their application, following with discuss at the challenges.

Abstract: The elastic and thermodynamic properties of CdTe are studied under a pressure up to 8GPa and at a temperature range of 0~900K, by density functional theory as well as quasi-harmonic Debye model. The calculated bulk modulus B and its derivative B' are consistent with the values fitted according to Debye model, which confirms the applicability of Debye model to CdTe. Heat capacity Cv , Grüneisen parameter and thermal expansion coefficient decrease with pressure, but increase with temperature. It is an opposite case for Debye temperature . The results may be instructive for CdTe to be applied in extreme conditions.

Abstract: The direct energy band gap in the range of ~1.5eV and the high absorption coefficient (~105cm-1) makes Cadmium Telluride (CdTe) a suitable material for fabrication of thin film solar cells. Thin film solar cells based on CdTe (~ 1cm area) achieved efficiency of 15.6% on a laboratory scale. CdTe thin films were deposited by thermal evaporation technique under vacuum 2×10-5mbar on glass and stainless steel (SS) substrates. During deposition substrates temperature was kept same at 200C for all samples. The structural properties were determined by the X-ray Diffraction (XRD) patterns. All samples exhibit polycrystalline nature. Dependence of different structural parameters such as lattice parameter, micro strain, and grain size and dislocation density on thickness was studied. Also the influence of the different substrates on these parameters was investigated. The analysis showed that the preferential orientation of films was dependent on the substrate type.

Abstract: Sb layered Te/Cd thin films have been prepared by using Stacked Elemental Layer (SEL) method. The presence of mixed phases (CdTe and Sb2Te3) in the films was confirmed by the x-ray diffraction technique. The calculated structural parameters demonstrated the feasibility of Sb doping via SEL method. The topographical and electrical studies of the synthesized thin films depicted the influence of Sb on both surface morphology and conductivity. The values of conductivity of the annealed films were in between 2 x 10-3 and 175 x 10-2 Scm-2. A desired chemical composition of films was confirmed from spectrum shape analysis using energy dispersive x-ray.

Abstract: This paper describes the synthesis of CdTe and CdTe/CdS core-shell quantum dots (QDs) in aqueous solution. The quantum dots are prepared by using thioglycolic acid (TGA) as stabilizers. The synthesis procedure is simple and controllable. Different sized CdTe QDs with tuned PL wavelengths from 550 to 640 nm was synthesized by controlling reaction time within 5 h in aqueous solutions at a temperature of 100 °C. We also investigated the influence of precursor Cd/Te molar ratio for the prepared QDs. It was showed that the core-shell CdTe/CdS QDs have larger photoluminescence (PL) emission intensity than the original CdTe QDs. The synthesized core-shell CdTe/ZnS QDs have high quality, water-soluble and will be useful in applications of biolabeling, biosensing, and imaging.

Abstract: An environmentally friendly synthesis was developed to fabricate aqueous CdTe quantum dots (QDs) using thilglycolic acid (TGA) as a capping agent. Optimal preparation conditions including pH (11.2) and TGA/Cd molar ratio (1.5:1) resulted in CdTe QDs with high photoluminescence (PL) quantum yield up to 56%. The TGA-capped CdTe QDs exhibited tunable PL from green to red. Lifetime measurement indicated that the average lifetime of the TGA-capped QDs increased with increasing their sizes (27.5 and 37.2 ns for the QDs with PL peak wavelength of 607 and 636 nm, respectively). The PL of the QDs revealed the dependence of temperature, in which the QDs exhibited a red-shifted PL peak with increasing temperature. Such PL behavior depended strongly on the QD sizes.

Abstract: Novel hybrid SiO₂-coated CdTe core-shell nanocrystals (NCs) were fabricated by re-dispersing green-emitting CdTe NCs in a solution of Cd²⁺ ions, thioglycolic acid (TGA), tetraethyl orthosilicate and ammonia with a sol-gel reaction at room temperature and a further reflux procedure. The hybrid NCs consisted of a CdTe core and a hybrid SiO₂ shell with CdS-like clusters. The clusters created by the reaction of Cd²⁺ and S^2- generated by the decomposition of TGA during reflux. The hybrid NCs exhibited tunable photoluminescence (PL) color from green to red and high PL quantum yield (PLQY). The CdS-like clusters play an important role for the hybrid NCs with numerous PL properties. Compared with initial CdTe NCs, the PLQY of the hybrid NCs increased from 18% to 47% together with a red-shifted PL peak wavelength of 61 nm. The average lifetime of the hybrid NCs (39 ns) is longer than that of initial CdTe NCs (25 ns). The high PLQY and the hybrid shell make CdTe NCs an important application for biological technique.

Abstract: Because of the good photoelectric learning properties and chemical properties, CdTe nanocrystalline as an important Ⅱ-Ⅵ clan semiconductor materials has been used in LEDs, photonics, in aspects of materials and biomarker and so on. W/O microemulsion method has the peculiarity of tester simpleness, easy manipulation, room temperature react etc. In this paper CdTe nanoparticles was synthesized in CTAB/cyclohexane/isobutanol/water quatemary microemulsion system in alkaline condition and nitrogen. The morphology of the final products were characterized by X-ray power diffraction, transmission electron microscopy. according to the means, this paper researches the effect of surfactant contentration to morphology. The result is that the different morphology can be obtained through the different CTAB concentration. Finally, according to TEM chart, this paper infers the formation mechanism of the CdTe.