Synthesis of polymer–PbS nanocomposite by solar irradiation-induced thermolysis process and its photovoltaic applications

In this study, we report the development of a new route for the synthesis of polymer–PbS nanocomposite thin film by a novel solar irradiation-induced reaction which is completely free from any complexing agents and toxic chemicals. The as synthesised polymer–PbS thin films were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–Vis absorption spectroscopy. The optical studies showed a direct allowed band gap of PbS lying in the range 1.78–2.2 eV. The XRD pattern shows the cubic structure of PbS with a lattice parameter of 5.927 Å. The SEM micrograph of the as-synthesised PbS thin films shows clusters in a relatively loose compact structure in the poly(vinyl alcohol) matrix and separated by voids, which are clearly observed in the surface. However, after annealing, most of the voids disappear in the PbS surface and it is likely that the clusters coalesce giving rise to an homogeneous and compact film. The PbS thin film after annealing is almost pinhole free and as such suitable for application in solar cell. A proto-type thin film solar cell of CdS/PbS was fabricated (1 × 1 cm2) on glass substrates using this deposition technique for PbS. The CdS layer was deposited by heat-induced thermolysis technique. The current–voltage (I–V) characteristics of the cells were measured with a high-impedance (∼1014) ECIL electrometer amplifier (model EA812). The efficiency of the solar cell was found as 2.54%.