Abstract:
This thesis deals with the elaboration and characterization of lead sulfide films (PbS) for photovoltaic or infrared applications. We used the CBD chemical bath deposition method to synthesize these films, and this, for its simplicity and low cost. The deposit solution is composed of a lead salt and thiourea (CS(NH2)2) as sources of Pb and S, respectively.
Complexing agents are added to control the deposition rate and the pH of the bath. The
samples were prepared by varying several parameters: the nature of the Pb precursor, the concentration of thiourea in the bath, the pH of the bath, the mixture of two precursors of Pb,
the deposition time and doping by several elements (An Np's, Cu and Zn). The post deposited films were subjected to various characterizations: structural, morphological, optical and electrical. The structural characterization shows that the PbS film have a cubic structure with a preferential orientation along the (200) plane for moderate growth rate and changes to (111) plane for high rates. Optical characterization allowed us to note a significant broadening of
the optical gap up to 1.4 eV by quantum confinement effect for a relatively wide crystallites.
Measurements of the electrical conductivity of the films confirm that these materials are ptype and have a good conductivity in particular for films doped with Au nanoparticles. I-V characteristics of heterostructures PbS/CdS/FTO and PbS/ZnS/FTO made from films prepared according to the studied experimental conditions, show that thermal annealing significantly affects the leakage current of the structures studied. Photoelectric effect for the PbS/ZnS/FTO cell, based on co-doped Zn-Au PbS absorbent film, was observed. Calculations show relatively low characteristic values of short circuit current density, open circuit voltage and efficiency. These values are respectively equal to 5.84 mA / cm2, 417mV and 0.84%. We performed sensitivity tests of PbS films to infrared radiation. Thin films PbS are very sensitive to heat emitted by a hot body. The response of the PbS detector, by measuring R, upon exposure to IR radiation is linear, instantaneous and reproducible.
