Characterization of ZnS thin films synthesized through a non-toxic precursors chemical bath

• High quality ZnS thin films have been deposited by chemical bath deposition technique from a non-toxic precursor’s solution.
• Nanocrystalline ZnS thin films with large band gap energy were synthesized without using ammonia.
• Evidence that the growing of the thin films is carried out by means of hydroxide mechanism was found.
• The properties of these ZnS thin films are similar and in some cases better than the corresponding ones produced using toxic precursors such as ammonia.

In solar cells, ZnS window layer deposited by chemical bath technique can reach the highest conversion efficiency; however, precursors used in the process normally are materials highly volatile, toxic and harmful to the environment and health (typically ammonia and hydrazine). In this work the characterization of ZnS thin films deposited by chemical bath in a non-toxic alkaline solution is reported. The effect of deposition technique (growth in several times) on the properties of the ZnS thin film was studied. The films exhibited a high percentage of optical transmission (greater than 80%); as the deposition time increased a decreasing in the band gap values from 3.83 eV to 3.71 eV was observed. From chemical analysis, the presence of ZnS and Zn(OH)2 was identified and X-ray diffraction patterns exhibited a clear peak corresponding to ZnS hexagonal phase (1 0 3) plane, which was confirmed by electron diffraction patterns. From morphological studies, compact samples with well-defined particles, low roughness, homogeneous and pinhole-free in the surface were observed. From obtained results, it is evident that deposits of ZnS–CBD using a non-toxic solution are suitable as window layer for TFSC.

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