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Olivia Rodgers

Abstract

The addition of embedded silver (Ag) nanoparticles in cadmium sulfide/cadmium telluride thin films deposited on ITO (indium tin oxide) have been investigated in this study. Due to the addition of silver nanoparticles, incoming light will be scattered and trapped thus enhancing absorption and increasing the amount of electron and hole pairs being created by absorbed photons. Solar cells with Ag nanoparticles (NPs) will produce a larger electrical current compared with a solar cell made with the absence of metal nanoparticles. The inclusion of metal nanoparticles and its effect on light scattering and excitation of surface plasmon resonances within the active layer of the solar cell was examined. It was also studied if the light scattering and excitation of surface plasmon resonances were dependent on the size and shape of NPs and how the Ag NPs will affect the overall photovoltaic conversion efficiency of the thin films. In the process of creating these cells, CdTe (cadmium telluride) and CdS (cadmium sulfide) are deposited by the method of Pulsed Laser Deposition (PLD) onto ITO coated glass substrates. Ag nanoparticles were deposited between the CdS layer and the CdTe layer by the use of PLD method with various deposition parameters and durations to obtain variations in nanoparticle coverage at the interface. In order to structurally characterize the silver nanoparticle embedded thin films, scanning electron microscopy (SEM), x-ray diffraction ellipsometry, energy dispersive x-ray spectroscopy (EDX), and atomic force microscopy (AFM) were used. The photovoltaic measurements were performed by LabVIEW assisted Keithley SourceMeter. The photovoltaic conversion efficiency exhibits a sensitive dependence on the size and the particle density of the embedded Ag nanoparticles. The variation of the silver particle size and particle density on the structure and the electrical performance of the thin films will be discussed.

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