Optical and structural study of In₂S₃ thin films growth by co-evaporation and chemical bath deposition (CBD) on Cu₃BiS₃

Highlights: • In₂S₃ thin films usually grow like an ultrathin. • Samples grown by CBD have a higher degree of coverage of the substrate unlike co-evaporation method. • Solar cells of Al/TCO/In₂S₃/Cu₃BiS₃/Mo structure. • In₂S₃ thin films were deposited on Cu₃BiS₃ (CBS), with of In₂S₃ β-phase with tetragonal structure. - Abstract: We present the growth of In₂S₃ onto Cu₃BiS₃ layers and soda-lime glass (SLG) substrates by using chemical bath deposition (CBD) and physical co-evaporation. The results reveal that the microstructure and the optical properties of the In₂S₃ films are highly dependent on the growth method. X-ray diffractrograms show that In₂S₃ films have a higher crystallinity when growing by co-evaporation than by CBD. In₂S₃ thin films grown by CBD with a thickness below 170 nm have an amorphous structure however when increasing the thickness the films exhibit two diffraction peaks associated to the (1 0 3) and (1 0 7) planes of the β-In₂S₃ tetragonal structure. It was also found that the In₂S₃ films present an energy bandgap (E_g) of about 2.75 eV, regardless of the thickness of the samples