Novel chemical route for chemical bath deposition of Cu2ZnSnS4 (CZTS) thin films with stacked precursor thin films

• CZTS films were fabricated by using stacked CBD layers.
• The pH adjustment was crucial to avoid peeling-off of films.
• The CBD films after post-sulfurization showed pure CZTS phase.
• Band gaps of CZTS films were 1.48–1.51 eV.

A new chemical route for chemical bath deposition was proposed for deposition of Cu2ZnSnS4 (CZTS) thin films. Two stacking sequences SLG/SnS/CuS/ZnS and SLG/ZnS/CuS/SnS were demonstrated for chemical bath deposition of CZTS film. We found that peeling-off during stacking films can be solved by adjusting pH value of solution. The CBD CZTS films were followed by subsequent sulfurization to improve crystal quality. The post-sulfurized films showed kesterite crystal structure with large crystalline grains, which was confirmed by Raman spectroscopy and X-ray diffraction. The band gap energies of CZTS films were estimated to be 1.48–1.51 eV, which are promising for solar cell application.