Heat treatments in chemically deposited SnS thin films and their influence in CdS/SnS photovoltaic structures

摘要

Chemical deposition technique is used to produce good quality tin sulphide (SnS) thin films of 450 nm in thickness, from a chemical bath containing tin chloride (SnCl_2·2H_2O) and thioacetamide. The SnS thin films were annealed at 300, 350 and 400 ℃ for 1 h in vacuum, nitrogen and argon atmospheres, resulting in the modification of their optical and electrical properties. The optical band gap showed a decrease from 1.2 to 1 eV whereas the electrical conductivity increased by more than two orders in the heat treated films at 400 ℃ in comparison with those of pristine samples. The morphology analysis of the as prepared and heat treated SnS thin films was done using scanning electron microscopy; X-ray diffraction patterns showed orthorhombic SnS phase and the chemical states of the elements were confirmed by X-ray photoelectron spectroscopy. The heat treated SnS thin films (1.8 μm thickness) were incorporated to photovoltaic structures of the type: Glass/TCO/CdS/SnS/C/Ag, showing open circuit voltages (V_(oc)) from 270 to 330 mV and a short circuit current density (J_(sc)) up to 6 mA/cm~2.