New p-type absorber films formed by interfacial diffusion in chemically deposited metal chalcogenide multilayer films

We report on new p-type ternary metal chalcogenide absorber films for possible solar energy applications. The films are formed by interfacial diffusion in chemically deposited multilayer films: CuS films (0.15 - 0.6 micrometer) deposited on ZnS, PbS or Bi2S3 films (approximately equal to 0.1 micrometer). The diffusion takes place during annealing at temperatures above 150 degree(s)C and is shown in the XPS depth profile spectra of the annealed samples: metal atoms (Zn, Pb or Bi) of the underlying substrate films are detected at the surface layers after the annealing. The peculiarity of the multilayer films is that they show almost constant sheet resistance upon further annealing until 350 degree(s)C. The sheet resistances are in the range of 20 - 100 (Omega) suggesting conductivities (p-type) of up to 400 (Omega) -1cm-1. In the case of CuS on Bi2S3 films, the formation of a compound, Cu3BiS3, is clearly detected.