Electrodeposited CuInSe2 Thin Film Junctions
We have investigated thin films and junctions based on copper indium diselenide (CIS) which have been grown by electrochemical deposition. CIS is a leading candidate for use in polycrystalline thin film photovoltaic solar cells. Electrodeposition is a cost-effective method for producing thin-film CIS. We have produced both p and n type CIS thin films from the same aqueous solution by simply varying the deposition potential. A CIS pn junction was deposited using a step-function potential. Stoichiometry of the single layer films was determined by energy dispersive spectroscopy. Carrier densities of these films increased with deviation from stoichiometry, as determined by the capacitance versus voltage dependence of Schottky contacts. Optical bandgaps for the single layer films as determined by transmission spectroscopy were also found to increase with deviation from stoichiometry. Rectifying current versus voltage characteristics were demonstrated for the Schottky barriers and for the pn junction.
Atmospheric Pressure Spray Chemical Vapor Deposited CuInS2 Thin Films for Photovoltaic Applications
Solar cells have been prepared using atmospheric pressure spray chemical vapor deposited CulnS2 absorbers. The CulnS2 films were deposited at 390°C using the single source precursor (PPh3)2Culn(SEt)4 in an argon atmosphere. The absorber ranges in thickness from 0.75 - 1.0 #m, and exhibits a crystallographic gradient, with the leading edge having a (220) preferred orientation and the trailing edge having a (112) orientation. Schottky diodes prepared by thermal evaporation of aluminum contacts on to the CulnS2 yielded diodes for films that were annealed at 600°C. Solar cells were prepared using annealed films and had the (top down) composition of AI/ZnO/CdS/CulnS2/Mo/Glass. The Jsc, Voc, FF and q were 6.46 mA/cm 2, 307 mV, 24% and 0.35%, respectively for the best small area cells under simulated AM0 illumination.
Microstructure of the solder-casting zone in bridges of dental gold alloys.
The composition and structure were studied in the cast and in the solder of bridges which had failed clinically. Both materials were gold alloys but with different contents of Pt, Ag and Zn. The metallographic investigation revealed defects mostly in the solder, situated in the subsurface layer. SEM studied of the fracture surface revealed large porosites and a structure of dense parallel lines--striations--, indicating that the material had failed from fatigue. The materials in the fractured bridges were identified by micro-probe measurements. It was stated that cast material and solder material used together, were of different composition.