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Currently, different shapes and sizes of silver and gold nanoparticles are being studied in many fields of plasmonic energy harvesting device including plasmonic solar cells due to their unique plasmonic properties, particularly in the visible and NIR-region (400-1200 nm). In this experiment, Finite Element Method is used to study the absorption, scattering and extinction spectra of the metal nanoparticles for better understanding of plasmonic effects with the application of COMSOL Multiphysics. Furthermore, the influences of the nanoparticle size, geometry and surrounding dielectric medium on the plasmon resonance peak of the metal nanoparticle is studied using the same software and the results are being analysed in this paper. It is observed that optical absorption and the plasmon peaks can be adjusted by altering sizes and shape of nanoparticles in order to obtain the desired level of absorption. Other parameter such as correlation of multipole resonance with the dipole resonance is also being presented. Key interesting phenomenon which is detected during this experiment is that Ag nanoparticle as its size increases beyond 50 nm, exhibits a multipole resonance peak in the near UV region in addition to the dipole resonance peak, whereas the same is not observed in the case of Au nanoparticle. The origin of this multipole resonant peak shall be further discussed along with its applicability to design efficient plasmonic devices.
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