Sputtered CuInSe2 polycrystalline and epitaxial films and devices

Recent solar cell fabrication results based on a scalable hybrid sputtering and evaporation deposition process are described. A method for controlling adhesion problems, which are a major cause of poor device performance is presented based on a two-phase back contact substrate metallization; and results of transmission electron microscopy analyses of epitaxial CuInSe₂ are described. Polycrystalline CuInSe₂ was deposited on Mo or Cu-Mo coated glass. Single crystal CuInSe₂ was grown on GaAs substrates. The use of Cu-Mo two phase back contacts significantly improved adhesion of our CuInSe₂ films to the substrates. The best heterojunction solar cell produced to date on Cu-Mo has an efficiency of 10.0%. Cell performance uniformity was also improved relative to results on pure Mo. Single crystal CuInSe₂ grown on GaAs (111)A substrates showed very rough surface morphologies. Films on GaAs (111)B were smooth with occasional triangular pyramidal islands. The most stable faces of CuInSe ₂ are concluded to be the Se-terminated (112) planes