In₂S₃ Thin Films Produced by Thermal Evaporation for Solar Cell Applications

In₂S₃ thin films were prepared on glass substrates. X-ray diffraction spectra showed that the In₂S₃ thin films showed amorphous structures before annealing and tetragonal structures after annealing up to 400 °C were preferentially grown along the (220) orientation. The crystal structure was defective spinel (tetragonal) with lattice constants of a = 7.62 Å and c = 32.33 Å. Energy band gap of the layers have been calculated from the optical transmittance data in the wavelength range 500–2000 nm. The optical transmittance of the films was decreased from 82% to 64% and the band gap varied in the range of 1.93–2.95 eV depended on preparation conditions. The AFM topography images also clearly different surface profile of these thin films. Grain size and roughness of the thin films was greatly decreased after annealing. An annealing temperature of 400 °C during 60 min was the optimal conditions.