Effect of indium doping on physical properties of nanocrystallized SnS zinc blend thin films grown by chemical bath deposition

Abstract

SnS:In thin films have been successfully prepared on Pyrex substrates using low cost chemical bath deposition technique with different indium concentrations (y=[In][Sn]=4%,6%,8%,and10%). The structure, the surface morphology, and the optical properties of the SnS:In films were studied by x-ray diffraction, scanning electron microscope, atomic force microscopy, and spectrophotometer measurements. In order to obtain a thickness of the order of 308 ± 10 nm for potential applications in solar cell devices, a multilayer deposition has been prepared. It is found that the physical properties of tin sulphide are affected by indium concentration. In fact, x-ray diffraction study showed that better crystallinity in zinc blend structure with preferential orientations (111)ZB and (200)ZB was obtained for y equal to 6%. According to the AFM analysis, we remark that low average surface roughness value of SnS(ZB) thin film is obtained with In concentrations equal to y = 6%. Energy dispersive spectroscopy showed the existence of In, Sn, and S in the films. Optical analyses by means of transmission T(λ) and reflection R(λ) measurements show 1.57 eV as an optical band gap value of SnS:In(6%), which is lower than the previously obtained value (1.76 eV) for undoped tin sulphide. In doped tin sulphide exhibits a high absorption coefficient 2.5 × 106 cm−1, indicating that SnS:In can be used as absorber thin layer in photovoltaic structure such as SnS:In/ZnS/SnO2:F and SnS:In/In2S3/SnO2:F, where ZnS and In2S3 are chemically deposited as described in a previous work. In this study, the hetero-junctions SnS/In2S3:Al and SnS/ZnS:In are also investigated.