547 research outputs found
The role of transparent conducting oxide and glass substrate in the performance of CdTe/CdS thin film solar cells
No full textA study of high temperature interaction benveen the glass substrate and several types of TCO and the TCO and CdS films is reported. We found out that the most suitable TCO, when a soda-lilne glass is used as a substrate, are Cd2SnO4 and fluorine doped In2O3; CdTe/CdS solar cells with efficiency around 14% and a high stability can be prepared on these kinds of TCO if Sb2Te3 is used as a back contact for CdTe
Cadmium and Zinc Chloride Treatments of CdS Films for the Preparation of High Efficiency CdTe/CdS Thin Film Solar Cells
No full textCdTe/CdS thin film solar cells exhibiting conversion efficiency dose to 14% have been prepared on glass substrates by treating the CdS film with ZnCl2 and CdC2. This treatment has shown to be effective in rendering the CdS film less reactive with CdTe when this is deposited on top of CdS by Close Spaced Sublimation at a substrate temperature of 500-520°C. This limits the interdiffusion between CdS and CdTe during the cell preparation and improves both the open-circuit voltage and fill factor of the solar cell
A highly efficient and stable CdTe/CdS thin film solar cell
No full textIn this paper we describe the fabrication and characteristics of highly efficient and stable CdTe/CdS thin film solar cells. Our cells are prepared in three subsequent phases. Firstly, we deposit via sputtering, without solution of continuity a layer of CdS on top of the front contact made up of a double layer of ITO/SnO2 deposited on a soda lime glass substrate. The second phase consists in the treatment of the CdS layer, which is the key factor for the fabrication of a good heterojunction, with CdCl2 and in the subsequent deposition of the CdTe layer via close space sublimation technique. Finally, the back contact is fabricated via sputtering making use of the Sb,Te, compound which guarantees the cell stability. Under global AM1.5 conditions the open-circuit voltage, short-circuit current and fill factor of our best cell, fabricated without antireflecting coating and normalized to the area of 1 cm(2), were V-oc = 858 mV, J(sc) = 23 mA/cm(2) and ff = 74%, respectively, corresponding to a total area conversion efficiency of eta = 14.6%. (C) 1999 Elsevier Science B.V. All rights reserved
A Three Stage Selenization Process for the Preparation of High Efficiency CuGaInSe2/CdS Thin Film Solar Cells
No full textCuGaInSe2/CdS thin film solar cell with an efficiency in excess of 15% have been prepared by a novel three stage selenization method. The first stage consists in the deposition of Cu, In, Ga elemental layer on Mo covered soda lime glass and selenization of the layers in a Se vapour. For the second and third stage only Cu and Ga are used as elemental layers in order to increase the amount of Ga in CuGaInSe2 film
High Efficiency and Stable CdTe/CdS Thin Film Solar Cells on Soda Lime Glass
No full textStable CdTe/CdS thin film solar cells which exhibit a conversion efficiency around 15% were prepared on soda lime glass substrates. These results were obtained by intervening on three important layers, which compose the cell namely the front contact, the CdS film and the back contact. The front transparent contact was prepared by depositing in sequence an Sn02 and an ITO film, the first one to passivate the glass against Na diffusion and the second one to get a low sheet resistance. CdS films deposited by sputtering were treated with CdCl2 at 500°C in air for 15 min. This treatment improves both the transparency and the crystallinity of the CdS film. Finally, as a back contact, Sb2Te3, which is a low gap compound exhibiting p-type conduction with a very low resistivity, was used. This contact secures the stability of the cell
Development of a Novel Precursor for the preparation by selenization of high efficiency CuInGaSe2/CdS Thin Film Solar Cells
No full textA novel precursor suitable to prepare uniform CuInGaSe2 thin films on an 1 inch2 area has been developed. The precursor is obtained by depositing in sequence In2Se3, Cu and Ga on a Mo covered glass and by a subsequent annealing at 400°C in vacuum for 1-2 hours. By selenizing this precursor in a Se-flux in vacuum for half an hour at 500°C substrate temperature a uniform and well crystallized CuInGaSe2 film is obtained. Solar cells prepared by depositing in sequence on top of the CuInGaSe2 film 60 nm of CdS, 100 nm of pure ZnO and 2 um of ZnO:Al exhibit a uniform efficiency of 14,5% over the 1 inch square area
Investigation on the capability of polysulphone for measuring biologically effective solar UV exposures
No full textPolysulphone (PS) dosimetry is a well-known technique broadly used to assess the erythemally effective solar UV dose received by anatomical sites (personal exposure). We investigate the capability of PS dosimetry to convert doses absorbed by PS badges into biologically effective solar UV exposures taking as examples two relevant effects for human skin: erythema induction and pre-vitamin D-3 production. PS calibration curves for erythemal and pre-vitamin D-3 were distinctly determined by using an empirical relationship between the biologically effective UV exposures and the PS absorbance change. This relationship is parameterized by a coefficient, distinct for each of the two considered biological effects, multiplying the same cubic polynomial function. It is shown how the multiplying coefficient is related to the ratio between the biologically effective and the PS weighted irradiances which is the prevailing factor affecting the accuracy of the calibration and, consequently, the capability of PS films for measuring biologically effective solar UV exposures. The points addressed in this paper can be extended to other biological effects of interest whose action spectra have some similarity with the PS film response
Back contacts to CSS CdS/CdTe solar cells and stability of performances
No full textHigh efficiency CdTe/CdS thin film solar cells with a good stability can be obtained if a low gap. high conductivity p-type semiconductor, such as Sb2Te3, is used as a back contact for CdTe. However, even though Sb2Te3 is used as a back contact, some cells can exhibit a low fill factor. This, at first sight, could suggest that the back contact is not the right one. Here we would like to show that a low fill factor could depend not only on the back contact but also on the front contact and on the amount of Na-diffusion from the soda lime glass substrate. (C) 2000 Elsevier Science S.A. All rights reserved
Growth ol polycrystalline CdS and CdTe thin layers for high efficiency thin film solar cells
No full textRecently, conversion efficiencies close to 16% for thin film solar cells based on the CdS/CdTe heterojunction have been reported. These relevant results, however, have not yet solved the problems which arise when industrial production is undertaken as the demand for low cost imposes constraints which considerably limit the final efficiency of the cells. In this paper, we will show that very high conversion efficiencies can still be achieved even making use of low cost soda-lime glass as substrate. In fact, the Na contained in this kind of glass diffuses during the fabrication of the cell into the active layers of the device causing a substantial decrease of the fill factor and consequently of the efficiency of the cell. In particular, we will describe the methods and the magnetron sputtering techniques used to grow a polycrystalline CdS thin film with a controlled Na content. We will also describe the details of the growth via the close-spaced sublimation (CSS) technique of the CdTe polycrystalline film, which are crucial for the heterojunction and the back contact which has been fabricated exploiting the characteristics of Sb2Te3 which is a low gap p-type semiconductor with a high conductivity. (C) 2000 Elsevier Science S.A. All rights reserved
Application of Current DLTS Technique for Study of Light Degradation in a-Si:H Solar Ceils
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