Alloyed Cu2Fe1-xBaxSnS4 for photoelectrochemical applications: band gap tailoring and structural transition

Cu2Fe1-xBaxSnS4 (CFBTS) thin films have been fabricated by the low-cost successive ionic layer and adsorption reaction (SILAR) method. The bandgap energies of CFBTS thin films are observed to be tuned from ~ 1.67 to ~ 1.94 eV in a linear manner with increasing Ba content (0 ≤ × ≤ 1). The crystal structure of CFBTS thin films are affected by the change in the Fe/Ba ratio. The structural transition from stannite to trigonal is found with the increased barium content in CFBTS from X-ray diffraction and Raman spectroscopy analysis. Sulfurized CBTS thin film exhibited pure trigonal phase without impurity peaks. Partial replacement of Fe with Ba in CFBTS alters the electronic structure of bulk CFBTS thin films, which affects charge separation and causes a change in band alignment. Finally, photo electrochemical studies were carried out for the as synthesised and the sulfurized samples.