Solution-processed photoactive trigonal Cu2BaSnS4 thin films for efficient solar energy harvesting

Cu2BaSnS4 (CBTS) is a new class of chalcogenide semiconductors that are recently studied as a promising photoabsorber to address the cationic disorder experienced in kesterite Cu2ZnSn(SexS1-x)4 (CZTSSe) materials. The quaternary CBTS thin films were developed via a simple sol-gel method on soda-lime glass substrates by spin coating technique. The XRD analysis showed a pure trigonal structure of CBTS and that the crystallinity of films increases as the sulfurization time increases. The Raman analysis showed a dominant peak at the 342 cm−1 regardless of the sulfurization time and can be assigned to the symmetric "A" mode of the lattice vibrations confirming the formation of trigonal CBTS. The optical band gaps were found to be decreased as sulfurization time increases and the optimal band gap value was found for the samples annealed over 20 min at 540°C. The longer sulfurization time (60 min) resulted in declined crystalline quality with formation of secondary phases. The shorter sulfurization time is optimal for the growth of pure phase CBTS films. The developed CBTS films were studied and exhibited photocurrent density of 2.02 mA/cm2 was measured at −650 mV from the photoelectrochemical J-V characteristics confirming the material is suitable for the water splitting applications.