Synthesis and characterization of hybrid solar cell based on zinc blend semiconductor quantum dots

An attempt have been made to synthesise and characterize of undoped and doped zinc blend based semiconducting quantum dots prepared by a simple wet chemical precipitation method for solar cell application. Formation of semiconducting quantum dot has been ascertained by X-ray diffraction (XRD), UV-visible spectroscopy, transmission electron microscopy (TEM) and impedance spectroscopy measurements. XRD studies confirm that all the prepared samples are in zinc-blende phase and in quantum dot regime. Dopants copper and cadmium cause a shift in diffraction peaks towards lower diffraction angles with linear increase in lattice constant values. UV-visible studies reveal decrease in optical bandgap of the QDs with co-doping of Cd and Cu ion in ZnS lattice though bandgap energy is higher than that of corresponding bulk material due to quantum confinement effect and alloyed formation of nanoparticles. TEM pictures reaffirm nanocrystalline nature of samples with size ranging 4 to 8 nm supporting XRD result. Mott-Schottky analysis revealed n-type conductivity of as prepared semiconducting QDs. To test the utility of these materials bulk heterojunction hybrid solar cells have been fabricated in 1 cmx1 cm size with p-type polypyrrole. Solar cells with quaternary zinc blend {(Zn0.85Cu0.15)(0.5)Cd0.5S} structure under AM 1.5 illumination resulted in highest conversion efficiency of 1.8% and fill factor 0.81.