Post-Deposition Sulfur Incorporation into CuInSe2 Thin Films

The effect of initial film composition and substrate in the sulfurization of CuInSe2 was investigated. CuInSe2 films deposited on either soda-lime glass (SL) or Corning 7059® borosilicate glass (7059) substrates were reacted in flowing H2S for times from 1 to 8 hours. Films with Cu-rich composition, Cu/In> 1, reacted for 1 hour had nearly all the Se replaced by S. For Cu-poor films the incorporation of S was significantly reduced. In addition, in Cu-poor films on SL glass CuInS2 and NaInS2 were found at the film surface. These phases were not detected in films on 7059 substrates or in Cu-rich films. A phenomenological model is proposed to explain the formation of segregated surface phases in Cu-poor films on SL substrates