The metal dopants in PbS thin films make a significant impact on its optical and electronic transport properties that make it useful for photovoltaic and other optoelectronic applications. The photovoltaic properties of Zn-doped nanostructured PbS thin films synthesized from zinc acetate, lead acetate, and thiourea as an absorber layer prepared using chemical spray pyrolysis were investigated. Rutherford backscattering spectroscopy (RBS), X-ray diffraction (XRD), and UV-visible spectrophotometry techniques were used to obtain stoichiometry, thickness, structural, and optical properties of the thin films before fabrication of Zn-PbS/CdS solar cell. The RBS revealed the stoichiometry ratio as Zn x Pb 1−x S and thickness range of 189.05-251.64 (10 15 atoms/cm 2). The inclusion of the Zn dopant drastically reduced the concentration of lead from the initial 40.93-14.95%. Optical analysis of the films gave high optical absorption and relatively low reflectance from visible toward the NIR region. An increase in energy bandgap was observed with Zn dopants inclusion from 0.53 to 1.65 eV, which fits the path of the solar radiation for maximum absorption. Photovoltaic properties revealed from the J-V measurement confirmed that Zn-doped sample 6% ZnAcet thin film solar cell gave a maximum short-circuit current density (J sc) of 17.30 mA/cm 2 , open-circuit (V oc) 390 mV, fill factor (FF) 0.48, and conversion efficiency (η) of 2.7%.
A simple model has been used to investigate the nature of chemical order in Na-Pb and Na-Hg liquid binary alloy at 700K and 673K respectively. The energy parameter obtained from the model was used to calculate the concentration dependent mixing properties such as Gibb's free energy of mixing, Concentration fluctuations in the long wavelength limit and the Warren-Cowley chemical short range order parameter. Results obtained showed that both alloys are heterocoordinated throughout the entire concentration and there is tendency for segregation and demixing to take place in the liquid alloys. We observed that Na-Hg liquid alloy is more strongly interacting binary alloy and chemically ordered than Na-Pb liquid alloy.
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