We have been investigating the synthesis of novel materials and device structures based on CuInSe2 or CIS system We are interested in developing CIS for use in thin film photoltaic solar cells used in space power systems. Non-stoichiometric native defects allow CIS to be selectively doped n or p type by controlling the Cu to In ratio. The Cu to In ratio of an electrodeposited CIS thin film is shown to be directly proportional to the deposition voltage. This behavior has allowed us to deposit different semiconductor-type films, pn junctions, and multilayer structures from the same aqueous solution. The affect of annealing in an Argon atmosphere and the addition of a wetting agent to our deposition solutions on the structural and electrical behavior of our films was measured. A dramatic improvement in the crystallinity, which was proportional to the annealing temperature was observed. The addition of a wetting agent to the solution was shown to improve the surface morphology and provide uniformity in the grain size. The electrical characterization of Schottky barriers on the CIS showed a decrease in several orders of magnitude of the carrier density with annealing. The ability to incorporate our CIS-based films in pn junction devices using CdS window layers was demonstrated by the rectifying current versus voltage behavior of these junctions.