Industrial Upscaling of CdTe/CdS Thin Film Solar Cells

CdTe/CdS thin film solar cells, since they are made with easily scalable techniques such as sputtering and closed space sublimation, can be considered particularly suitable to be produced on a large scale. Besides, we developed a new process which is simplified in respect to the normally used processes, since it is dry and it does not make use of any acid. Furthermore, CdCl2, used for CdTe treatment, has been substituted with a non toxic gas, namely HCF2Cl. Back contact is done by a procedure that allows to make stable cells. An efficiency close to 16% is obtained on 1 cm2 area with this process. In order to scale up this new process to an industrial production, a new company, named ARENDI, with the participation of the Marcegaglia industrial group, IFIS Bank of Venice, the contribution of Ministry of Environmental and the scientific support of the thin film group of the University of Parma, has been constituted. The line is starting to be constructed near Milan and will be ready within two years. The size of the module will be 60x120 cm2 and the production capacity of the line should be around 15 MW/year

A study of the CdTe treatment with a Freon gas such as CHF2Cl

In order to obtain high efficiency CdS/CdTe solar cells, a CdTe heat treatment in a Cl-2 containing atmosphere is necessary. Normally, this treatment is done by depositing a CdCl2 thin film on top of CdTe and by heating the system in air at a fixed temperature. This step is disadvantageous in a large scale fabrication process because it involves the use of CdCl2 that it is difficult to be handled. We replaced this treatment by using a gas (HCF2Cl) that is stable, inert and not toxic at room temperature and eliminates the step of CdCl2 evaporation and subsequent chemical etching. (c) 2007 Elsevier B.V. All rights reserved

Development of low temperature approaches to device quality cds: a modified geometry for solution growth of thin films and their characterisation.

Cadmium sulphide thin films have been grown using a modified chemical bath deposition method with four innovative features: i) ethylenediamine was used as the complexing agent, enabling the use of low cadmium concentrations, ii) a rectangular bath geometry with heated glass plate walls was employed, iii) a low deposition temperature (30 degrees C) was used and iv) nitrogen gas was flowed over the substrate surface during growth. The latter two features eliminate the formation and adherence of gas bubbles on the substrate during growth, hence reducing pinhole formation. On inspection, films were found to be specularly reflective and homogeneous with no visible pinholes. Characterisation was performed by atomic force microscopy, grazing incidence X-ray diffraction, optical transmittance and photoluminescence spectroscopy. It was shown that films possessed a low surface roughness value of 5.2 nm, were highly crystalline, textured, had a grain size of 15 nm and a bandgap of 2.42 eV Preliminary results from CdTe/CdS thin film photovoltaic devices demonstrate a notable efficiency of 9.8%. (c) 2006 Elsevier B.V. All rights reserved