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1

Electrical characterisation of CdTe/CdS photovoltaic devices

100%

Wimbor M. , Romeo A. , Igalson M.

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tom Vol. 8, No. 4

375-377

EN

Thin film solar cells based on Cd/Te/Cds are expected to become the base material for the low - cost and efficient large-scale solar energy conversion devices. The samples have been investigated using current-voltage (I-V) and capacitance-voltage (C-V) measurements in order to define the transport mechanism in heterostructure and basic electronic parameters. Trap-assisted tunnelling has been found to dominate carrier transport mechanism in the junction.

2

Reverse-bias DLTS for investigation of the interface region in thin film solar cells

88%

Igalson M. , Zabierowski P. , Romeo A. , Stolt L.

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tom Vol. 8, No. 4

346-349

EN

The interface states in TCO/Cds/CdTe and ZnO/CdS/Cu(In,Ga)Se₂ photovoltaic devices has been studied by use of reverse-bias transient capacitance spectroscopy. Laplace transform analysis has been used in order to enhance a spectral resolution of the technique. It is shown that the method yields useful information on the electronic characteristics of the heterointerface in the thin film solar cells. The conclusion include a degree of inversion of the heterointerface and a contribution of tunneling in the carrier transport. The influence of these factors on photovoltaic performance of the devices under study is discussed.

3

Surface strain during homoepitaxy : growth and ion ablation of CdTe

75%

Tatarenko S. , Etgens V. H. , Hartmann J. M. , Martrou D. , Arnoult A. , Cibert J. , Magnea N. , Sauvage-Simkin M. , Alvarez J. , Ferrer S.

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1999

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tom Vol. 7, No. 2

75-80

EN

Oscillations of the surface lattice parameter were observed by RHEED during the homoepitaxial growth of (001) CdTe by molecular beam epitaxy (MBE) and atomic layer epitaxy (ALE). The oscillations are associated to a deformation, induced by the surface reconstruction, at the free edges of the small 2D islands formed during the growth. In the same way, a lateral relaxation is measured during the layer by layer "de-growth" of (001) CdTe. Experiments using a CCD X-ray sensitive camera combined with the very bright X-ray beam offered by the European Synchrotron Radiation Facility allowed us to investigate the two layers behaviour of the CdTe surface in real time during the ablation by ion sputtering. The results show a relaxation mechanism, which is effective only whem islands are presented on the surface. A correlation has been found between the size the islands, their distribution, and the surface reconstruction. Particularly, a long-distance correlation between islands along the [1-10] direction has been observed.

4

Structural and luminescent properties of Fe3+ doped PVA capped CdTe nanoparticles

63%

Ravindranadh K. , Rao M. C.

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tom Vol. 35, No. 2

390--397

EN

During recent decades, magnetic and semiconductor nanoparticles have attracted significant attention of scientists in various fields of engineering, physics, chemistry, biology and medicine. Fe3+ doped PVA capped CdTe nanoparticles were prepared by co-precipitation method and characterized by powder X-ray diffraction, SEM, TEM, FT-IR, optical, EPR and PL techniques to collect the information about the crystal structure, coordination/local site symmetry of doped Fe3+ ions in the host lattice and the luminescent properties of prepared sample. Powder XRD data revealed that the crystal structure belongs to a cubic system and its lattice cell parameters were evaluated. The average crystallite size was estimated to be 8 nm. The morphology of prepared samples was analyzed by using SEM and TEM investigations. Functional groups of the prepared sample were observed in FT-IR spectra. Optical absorption and EPR studies have shown that on doping, Fe3+ ions enter the host lattice in octahedral site symmetry. PL studies of Fe3+ doped PVA capped CdTe nanoparticles revealed UV and blue emission bands. CIE chromaticity coordinates were also calculated from the emission spectrum of Fe3+ doped PVA capped CdTe nanoparticles.

5

Quantum dots for temperature sensing

54%

Doskaliuk N. , Lukan Y. , Khalavka Y.

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tom Vol. 2, Iss. 2

93--111

EN

Quantum dots are three-dimensional nanoparticles of semiconductors with typical sizes ranging from 2 to 10 nm. Due to the quantum confinement effect the energy gap increase with the size decreasing resulting in size-depended and fine-tunable optical characteristics. Besides this, the energy structure of a quantum dot with a certain size is highly sensitive to environmental conditions. These specific properties open a wide range of applications starting from optical and optoelectronic devices and ending with biosensing and life science. Temperature is one of those parameters influencing strongly on the optical properties of semiconductor nanocrystals, which make them promising materials for temperature sensing, more often using a fluorescent response. Compared to the conventional organic dyes already applied in this field, quantum dots exhibit a set of advantages, such as high quantum yield and photostability, long fluorescence lifetime, higher Stokes shift, and ability to surface functionalization with targeted organic molecules aimed to provide them biocompatibility. In this review, we briefly discuss the properties of II-VI and assumingly less toxic I-III-VI quantum dots, mechanisms of temperature-induced fluorescence response, and the feasibility of their practical application in the field of thermal sensing.