J. Sastré-Hernández

Physical properties of Bi2Te3 and Sb2Te3 films deposited by close space vapor transport

Near-stoichiometric bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3) films were grown by the close space vapor transport (CSVT) method in a relatively simple fashion. The dependence of the film properties on the substrate temperature was explored over a wide range by keeping the source-to-substrate thermal gradient fixed at 300 °C and 350 °C for the Bi2Te3 and Sb2Te3 film growth, respectively. A Seebeck coefficient (α) of 255 µV K−1 and a power factor of 20.5 × 10−4 W K−2 m−1 were obtained for Bi2Te3 at a substrate temperature of 350 °C; meanwhile, the maxima of the above parameters for the antimony telluride films (108 µV K−1 and 3.8 × 10−4 W K−2 m−1, respectively) were reached at a substrate temperature of 450 °C.

Improving the efficiency of CdS/CdTe solar cells by varying the thiourea/CdCl2 ratio in the CdS chemical bath

In this work, the influence of the properties of CdS thin films grown by chemical bath deposition upon the characteristics of CdS/CdTe solar cells, when varying the thiourea concentrations in the CdS bath solution, is studied. The important solar cell parameters such as short circuit current (Jsc), open circuit voltage (Voc), fill factor (FF) and efficiency (η) were measured and it was noted that they improve for thiourea/CdCl2 ratios (in the CdS deposition solution) up to 5, and drop for higher ratios in the range investigated. In addition, the ideal diode factor (n), saturation current (Jo) and series resistence (Rs) were studied under illumination and dark conditions. The results could be related to several factors, among them, the photoconductivity properties of the layers and the change of the CdS1−xTex layer at the CdS–CdTe interface.

Micro and Nano-Bricklayer Building Process of CDS Films: Their Optimal Applications in CDTE Solar Cells

For optimizing and having reproducibility of the PV-performance of CdTe based solar cells, the quality of the CdS-partner window material plays an important role. One of the main problems to be solved consists in eliminating the pinhole density in the CdS layer, as well as its processing with the suitable geometric granularity (grain size, roughness, barrier dimensions, voids and film thickness). We have started studying CBD-CdS bilayer deposition, as they make possible to get micro and nano CdS-particles, thus allowing us to engineer the particles size that could be embedded and recrystallized afterwards to improve the CdS film quality

Photovoltaic structures based on Cu(In, Ga)Se 2 thin films prepared by thermal co-evaporation

In this work, we are reporting the results of the deposition and characterization of Cu(InGa)Se2 thin films prepared by thermal co-evaporation and the results of the photovoltaic devices made with these Cu(In, Ga)Se2 thin films, using as the window material partner a CdS layer prepared from two different chemical bath solution recipes. Results have shown that high quality polycrystalline films have been obtained, which have very uniform morphology with grain sizes of tenths of a micrometer and a chemical composition very close to the stoichiometry of the Cu(In, Ga)Se2. After processing the Cu(In, Ga)Se2 thin film samples into solar cells, the highest conversion efficiency achieved was ∼ 11 %