Synthesis and Characterization of CdSe Quantum Dots for Photovoltaic Application

Nanomaterials and nanotechnology attained remarkable importance in the recent years. Nanomaterials have applications in diverse fields including chemistry, physics, material science, medicine, and engineering. Quantum dots (QDs) are semiconducting nanoparticles with particle size in the nanometer scale. QDs have typical diameters ranging from 1 to 10nm possess exceptional optical and electrical properties that makes them useful in photovoltaic, laser and light emitting diode (LED) applications. The band gap of QDs can be tuned by controlling the growth size and so the optical properties can be tuned in the visible range with broad excitation range. In our paper we synthesized and characterized CdSe quantum dots using hot injection method. We have successfully synthesized QDs of three different sizes ranging from 1 to 10nm in three sampling steps emitting in green, yellow and red region of the visible spectrum. Growth characteristics of QDs were studied by growing them at different temperatures and for different times than typical standard growth parameters. We attempted to synthesize QDs with varying sizes in one sampling step. The varying sizes were formed at 175^oC with multiple injections of Se in varying quantities. The fluorescence spectra showed three peaks at 482, 518 and 590nm respectively. The emission peaks indicating QDs of three different sizes, which was achieved by creating three nucleation steps by injecting controlled amounts of Se. Our QDs can be used in the photovoltaic application to improve the light absorption (broad wavelength) by the photo active material and to improve the charge carrier generation. We performed optical and electrical characterization using UV-Visible, fluorescence spectroscopy, cyclic voltammetry and Keithley. The crystallinity of QDs with different growth time was measured using X-ray diffraction (XRD) spectroscopy.