This report studies the influence of alkali elements (Na, K) to morphological, structural and optoelectronic properties of CIGS ceramic tile solar cell. Several ceramic enamels with altered chemical composition in terms of amount of alkali elements have been tested and compared. The influences of alkali type, its quantity and transfer mechanism have been investigated. The solar cell device has been assembled and characterized. The achieved results indicate that alkali elements (Na and K combination) modified the surface roughness and its diffusion from the enamel toward the absorber affect to the structural and final optoelectronic properties of the device. The alkali doping improve the Ga incorporation in the crystal lattice and an increasing in open circuit voltage (Voc) values, fill factor (FF) and the device efficiency. Optimal alkali quantities have been also determined. The best conversion efficiency is achieved for the cell with 4% wt Na 2 O and 3.2 % wt K 2 O (Eff. = 3,5 %), which presents an improvement of 30 % in efficiency relative to the standard (STD) solar cell sample chosen for comparative purposes.

In this work the use of porcelain stoneware tiles as alternative substrates for CIGS thin film solar cells for the development of specific applications as those related to building integration (BIPV, BAPV) are reported. Two types of porcelain stoneware have been compared: the conventional tile (STD) and the ecological tile (ECO). The ECO ceramic paste formulation has been designed adding industrial wastes (recycled glass, sludges and chamote). Chemical, technological and functional properties of the paste have been performed. The CIGS absorber has been synthesized by an easy and low-cost way of preparation using co-precipitation method. The solar cell device has been completed and fully characterized.The achieved results indicate better performances for ECO paste compared to the STD, stated in improved mechanical resistance, thickness and morphology. It is demonstrated 2 that both tiles are suitable for solar cell applications, but ECO substrate developed higher energy conversion efficiency of 1.3 %.

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As the production of ceramic porcelain stoneware in Spain is totally conditioned by the importation of ball clays, because of the lack of adequate Spanish ball clays, this work has focused on the formulation of ceramic porcelain body from Spanish clays purified by means of physical removal processes. This method was applied to three Spanish clays containing common clay impurities of iron (hematite and siderite) and organic matter. Iron removal was carried out using the wet sieve method, the hydrocycloning method and the electromagnetic filtering method, obtaining a reduction in iron content of up to 80 wt%, while the clay containing organic matter was treated thermally at 400ºC for 30 minutes so as to leave it almost completely purified. These treated clays, after being characterized (chemical and mineralogical composition, plasticity, organic carbon, thermal behaviour and colour), were used in the porcelain stoneware body composition instead of imported clays, the result being a composition capable of substituting the standard porcelain stoneware formulation in terms of sintering, morphology, colour, flexural strength and dilatometry.

In this research a mixture of 90%wt of industrial residues (recycled soda-lime glass and ashes from a coal power thermal plant) have been vitrified for their use as "secondary raw material". Then, a glaze suspension was prepared to be applied as a glaze suspension on the porcelain stoneware tile. The tested pieces have been fired by a conventional porcelain cycle at 1180ºC of maximum temperature. The XRD, XRF, SEM/EDS and the dilatometric analysis have been the instrumental techniques used to characterize the final material. Finally, an ecological glass-ceramic glaze perfectly fitting on porcelain ceramic tile has been produced, exhibiting a unique phase, anorthite, which ensures a high flexural strength (around 96 MPa) and a significant Vickers microhardness of 250 GPa, improving the mechanical properties of a conventional the porcelain ceramic tile.