Brazil has large, unelectrified, geographic regions with very high insolation throughout the year... more Brazil has large, unelectrified, geographic regions with very high insolation throughout the year. Development of solar energy research in Brazil evolved through establishment of well-equipped laboratories, spread of post-graduate education and basic research during 1958-72, intense applied research on solar thermal viz. collectors, refrigeration, furnaces, cookers, driers, and distillation; and photovoltaics viz. c-Si solar cells, Cu2S, CIGS, CdTe and a-
Conference Record of the Thirty-First IEEE Photovoltaic Specialists Conference - 2005, 2005
The properties of a material are affected by the orientations of individual grains, that is, by i... more The properties of a material are affected by the orientations of individual grains, that is, by its m icrotexture. Microtexture can be determined in a scanning electron microscope by analyzing the electron back-scatter diffraction pattems provided by the specimen. This work focuses upon microtexture determination in cadmium telluride thin films deposited by close spaced sublimation.
This work is focused on the activation of the photoconduction in lead sulfide (PbS) thin films de... more This work is focused on the activation of the photoconduction in lead sulfide (PbS) thin films deposited by chemical bath deposition (CBD). The films were chemically deposited from an aqueous solution of lead nitrate [Pb(NO 3 ) 2 ], sodium hydroxide (NaOH) and thiourea [SC(NH 2 ) 2 ]. Thirty minutes after immersing the substrates in the solution, the thickness of the film remained unchanged, suggesting that lead and sulphur ions had been fully consumed. Thus, thicker films were obtained depositing additional PbS from a fresh solution. The films were treated at 473 K under oxygen residual pressure of 1.33 Â 10 À 2 Pa. Photoconductivity measurements showed that the heat treatment activated the mechanism of photoconduction and the best results were obtained using two deposition steps.
This work investigates the microstructural changes-especially in grain boundary structure and gra... more This work investigates the microstructural changes-especially in grain boundary structure and grain orientation distribution-in CdTe thin films deposited by close spaced sublimation at low (LT) and high temperatures (HT) and submitted to a CdCl 2 heat treatment. These changes are quantitatively described by microtexture analysis, a spatial distribution of the orientation of the grains. The analysis is performed in a scanning electron microscope by means of identification of the electron backscattered diffraction patterns from individual grains. The texture of each grain, the misorientation between grains, and coincident site lattice boundary maps are obtained. The results show that the CdCl 2 treatment did not promote significant microstructural changes in HT-CdTe films, which grow with large and randomly oriented grains, and with a predominance of high-angle boundaries. On the other hand, for LT-CdTe films, this treatment promotes a substantial increase in grain size, a decreasing of preferential orientation, and an increase in the number of CSL and high-angle boundaries. These changes are considered to be a strong evidence for recrystallization.
Brazil has large, unelectrified, geographic regions with very high insolation throughout the year... more Brazil has large, unelectrified, geographic regions with very high insolation throughout the year. Development of solar energy research in Brazil evolved through establishment of well-equipped laboratories, spread of post-graduate education and basic research during 1958-72, intense applied research on solar thermal viz. collectors, refrigeration, furnaces, cookers, driers, and distillation; and photovoltaics viz. c-Si solar cells, Cu2S, CIGS, CdTe and a-
Conference Record of the Thirty-First IEEE Photovoltaic Specialists Conference - 2005, 2005
The properties of a material are affected by the orientations of individual grains, that is, by i... more The properties of a material are affected by the orientations of individual grains, that is, by its m icrotexture. Microtexture can be determined in a scanning electron microscope by analyzing the electron back-scatter diffraction pattems provided by the specimen. This work focuses upon microtexture determination in cadmium telluride thin films deposited by close spaced sublimation.
This work is focused on the activation of the photoconduction in lead sulfide (PbS) thin films de... more This work is focused on the activation of the photoconduction in lead sulfide (PbS) thin films deposited by chemical bath deposition (CBD). The films were chemically deposited from an aqueous solution of lead nitrate [Pb(NO 3 ) 2 ], sodium hydroxide (NaOH) and thiourea [SC(NH 2 ) 2 ]. Thirty minutes after immersing the substrates in the solution, the thickness of the film remained unchanged, suggesting that lead and sulphur ions had been fully consumed. Thus, thicker films were obtained depositing additional PbS from a fresh solution. The films were treated at 473 K under oxygen residual pressure of 1.33 Â 10 À 2 Pa. Photoconductivity measurements showed that the heat treatment activated the mechanism of photoconduction and the best results were obtained using two deposition steps.
This work investigates the microstructural changes-especially in grain boundary structure and gra... more This work investigates the microstructural changes-especially in grain boundary structure and grain orientation distribution-in CdTe thin films deposited by close spaced sublimation at low (LT) and high temperatures (HT) and submitted to a CdCl 2 heat treatment. These changes are quantitatively described by microtexture analysis, a spatial distribution of the orientation of the grains. The analysis is performed in a scanning electron microscope by means of identification of the electron backscattered diffraction patterns from individual grains. The texture of each grain, the misorientation between grains, and coincident site lattice boundary maps are obtained. The results show that the CdCl 2 treatment did not promote significant microstructural changes in HT-CdTe films, which grow with large and randomly oriented grains, and with a predominance of high-angle boundaries. On the other hand, for LT-CdTe films, this treatment promotes a substantial increase in grain size, a decreasing of preferential orientation, and an increase in the number of CSL and high-angle boundaries. These changes are considered to be a strong evidence for recrystallization.
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