Synthesis of CuIn(S,Se)₂ quaternary alloys by screen printing and selenization-sulfurization sequential steps: Development of composition graded absorbers for low cost photovoltaic devices

The viability of screen printing based processes followed by sequential sulfurization and selenization steps is investigated for the synthesis of both single phase and band gap graded CuIn(S,Se)₂ alloys. Process parameters as the temperature, time and order of the reactive thermal annealing for the chalcogen incorporation have a strong influence on the structure of the synthesized layers. Analysis of the processed layers show that formation of a band-gap graded layer with an S-rich surface region is promoted with an initial selenization step, while the use of an initial sulfurization step leads to formation of uniform Se rich CuIn(S,Se)₂ layers. These data demonstrate the potential of screen printing based processes for the synthesis of complex quaternary alloys for advanced photovoltaic applications.