Investigation of a stable Mo substrate for chalcopyrite solar cells: a green process for sustainable energy applications

Abstract

Abstract Molybdenum (Mo) films (~1 μm) as back contacts for chalcopyrite solar cells are usually deposited onto the glass substrate by DC-sputtering because of their high deposition rate with a column structure. During selenization, selenium (Se) is infiltrated deeply into the column structure of Mo films. Although the difference in sheet resistance and resistivity values before and after selenization is negligible, the selenized Mo films are easily peeled off from the glass substrate even with the tape testing. The existence of Se in Mo films with a column structure was investigated by scanning electron microscopy cross-section, energy-dispersive X-ray spectroscopy, and X-ray diffraction measurement. To overcome this obstacle, a 200-nm-thick Mo compact layer was deposited by RF-sputtering on top of the Mo film to prevent Se infiltration. Finally, the bilayer of Mo was passed with tape testing for both films before and after selenization. The results may be helpful to further achieve highly stable fabrication processes of chalcopyrite solar cells.