Gustavo A. Viana

Application of amorphous carbon based materials as antireflective coatings on crystalline silicon solar cells

We report on the investigation of the potential application of different forms of amorphous carbon (a-C and a-C:H) as an antireflective coating for crystalline silicon solar cells. Polymeric-like carbon (PLC) and hydrogenated diamond-like carbon films were deposited by plasma enhanced chemical vapor deposition. Tetrahedral amorphous carbon (ta-C) was deposited by the filtered cathodic vacuum arc technique. Those three different amorphous carbon structures were individually applied as single antireflective coatings on conventional (polished and texturized) p-n junction crystalline silicon solar cells. Due to their optical properties, good results were also obtained for double-layer antireflective coatings based on PLC or ta-C films combined with different materials. The results are compared with a conventional tin dioxide (SnO2) single-layer antireflective coating and zinc sulfide/magnesium fluoride (ZnS/MgF2) double-layer antireflective coatings. An increase of 23.7% in the short-circuit current density, ...

Structural, surface, and thermomechanical properties of intrinsic and argon implanted tetrahedral amorphous carbon

The structural, surface, and thermomechanical properties of intrinsic and argon incorporated tetrahedral amorphous carbon films deposited using the filtered cathodic vacuum arc process are reported. Argon atoms were simultaneously incorporated during the deposition of the films using an argon ion gun in the energy range of 0–180 eV. Contact angle measurements revealed that all of the deposited films are hydrophobic, regardless of the substrate bias voltage that was applied during the depositions. Thermal desorption spectroscopy measurements revealed that high argon bombarding energy favors films that are structurally more compact and thermally more stable. An investigation unbinding the mechanism of argon effusion and intrinsic stress relief is presented.

Effects of impurities concentration on the efficiency of solar cells manufactured with upgrade metallurgical silicon

In this work we reported the production of upgraded metallurgical grade silicon using a combination of different purification techniques, i.e., vacuum degassing, directional solidification and Czochralski growth. Chemical composition, resistivity and efficiency of silicon solar cells are presented. It was observed that those methods have different purification efficiency for different elements. The use of vacuum degassing is demonstrated to be a potential procedure to be used in a combination with other techniques to reduce impurities in metallurgical silicon as well as reduce the final price of the silicon wafers. The combination of vacuum degassing and Czochralski method provided upgraded metallurgical grade silicon. Solar cells efficiency approaching 10% was obtained using this material.