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8th World Conference on Photovoltaic Energy Conversion; 406-408, In this work, we study the growth of Sb2Se3 deposited by thermal evaporation on different buffer layers for superstrate configuration thin film solar cells. A comparison between CdS which has been widely used as a buffer layer and CdSe is represented. Selenium vacancies in Sb2Se3 thin film act as recombination centers, and according to the literatures, applying an excessive amount of Se improve the application of solar cell. By using CdSe as a buffer layer, selenium could diffuse into the film and it is supposed to increase the efficiency. In our case both devices show the same efficiency of around 3.5% and higher Jsc for CdSe device. Also, morphology results indicate slightly higher crystal quality for CdSe/Sb2Se3 thin film and the solar cells perform almost the same degradation results.

33rd European Photovoltaic Solar Energy Conference and Exhibition; 1221-1223, Tin sulfide is an excellent candidate for the mass production of solar cells as it is composed of abundant and not toxic elements. From our previous work on thermal evaporation of SnS solar cells, we now present SnS polycrystalline films by ionized jet deposition (IJD). This technology allows transferring atoms from a target of SnS to the substrate due to the generation of plasma from the target, giving enough energy to have a good crystallization of the material also at low temperature. SnS deposited by this technique show an incremented compactness, more robust thin film, which results to be less porous and more crystallized. Moreover the x-ray diffraction technique shows an improved stoichiometry with no secondary phases. Preliminary solar cells were made and indicate that IJD can be a good deposition technique for compounds with reduced congruent evaporation.

Synthetic garnet nanopowders of Y3Al5O12 (YAG) and Gd3Ga5O12 (GGG) were produced, and the occurrence of a broadband bright visible emission by nominally undoped YAG and GGG and Cr3+ doped GGG, depending on the environment pressure, as well as exciting on the pumping power, was demonstrated. The results indicate that high-intensity infrared laser irradiation in samples not only leads to heating (melting effects) but also produces visible broadband emission. Low pressure of the powders' environment favors the white light emission by lowering the threshold pumping power. A hypothesis on the nature of the emission is presented.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 1233-1236, In the past, we reported Cu(In,Ga)Se2 solar cells exhibiting an efficiency of about 16% obtained by sputtering and selenization, starting from targets of InSe, GaSe and Cu. Here, we report on the requirements, which have to be respected in order to get good precursors suitable to give high efficiency by simple selenization in a Se-vapour. First of all, the targets of InSe and GaSe should exhibit a density higher than 97% to avoid their damage during the sputtering deposition. Secondly, especially for InSe, the sputtering power has to be regulated. If it is too low then films with excess of Se are obtained and this can cause the peeling of the film during selenization. If the sputtering power is too high, segregation of In on the surface of the target is observed. We found out that the right sputtering power is about 3.8 W/cm2 corresponding to a deposition rate of ~ 20 Å/sec. Another important parameter is the substrate temperature. During the InSe deposition, if the temperature substrate is higher than 670 K then the film will contain In-excess. If the temperature is lower than 470 K the film can contain Se-excess. The substrate temperature is less critical when GaSe or Cu are deposited. In this case a higher substrate temperature, in the range 670 ÷ 720 K, is used in order to get a good mixing of InSe, GaSe and Cu. During the selenization, an important parameter to be considered is the deposition rate of Se. It has been found out that the grain size of the finished Cu(In,Ga)Se2 film is larger when the evaporation rate of Se is not too high and it is around 1 μm/sec. By controlling the above parameters, high quality Cu(In,Ga)Se2 films with a grain size larger than 1 μm are reproducibly obtained. These films, used to prepare solar cells, gave us the possibility to obtain an efficiency larger than 16%.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 263-266, The limited amount in nature of Te and In and the use of toxic elements like Cd and Se in CdTe and CuInGaSe2 solar devices (despite they have no effect on the environment) could be overcome with alternative thin films. SnS is one of the most promising materials due to its electrical and physical properties, but it is already demonstrated that high quality SnS thin films are required to enhance solar cells efficiency. In the present work, we have found out a threshold temperature, above which the absorber grows highly crystallized and compact avoiding the porous structure observed previously. The properties of this differently grown film is presented and compared with low substrate temperature layers. Moreover the study of a new post deposition treatment, which merges our CdCl2 methodologies with new non-toxic salts (KI or SnCl2), more suitable for SnS, is presented.

29th European Photovoltaic Solar Energy Conference and Exhibition; 1826-1828, In our laboratory we fabricate high efficiency CdTe solar cells, exceeding 15 % efficiency, with a low temperature process, where all the layers are deposited by vacuum evaporation with temperature below 450 °C. The CdCl2 treatment is typically prepared by putting drops of a methanol solution with a specific concentration of CdCl2. Starting from a previous work where we studied the effect of the different amount of CdCl2 by changing the methanol concentration, we have this time analyzed the recrystallization treatment by changing the annealing temperature from 310 °C up to 410 °C in air. By doing so we address the multiple effects that this process has on the material and device properties for CdTe solar cells. Activated CdTe layers have been analyzed by means of X-Ray diffraction spectroscopy and atomic force microscopy. Finished devices with efficiencies from 8% for the low temperature annealing up to more than 14% for the high temperature ones, have been analyzed by current-voltage, capacitance-voltage and drive level capacitance profiling techniques, showing that net carrier concentration is dependent with temperature. A detailed analysis of the formation of intermixed CdS/CdTe layer with temperature is also reported by external quantum efficiency.