Light Trapping using Anisotropic Plasmonic Nanoparticles

Abstract

The urge for a renewable energy source to take over the conventional fossil energy sources has always been a necessity. Thus a lot of work and effort has been spend on the photovoltaic cell research which focuses on conversion of solar energy into electrical energy. The studies in this field so far had classified the photovoltaic cells into first, second and third generation cells with the common single crystalline silicon solar cells being the first generation, thin film solar cells are the second generation and third generations consists of nanocrystalline materials, polymer materials, perovskite materials or some hybrid materials which give hopes on a cost effective as well as efficient production of a photovoltaic cell. Basically third generation solar cells are not limited by the Schottky-Queisser limit of power efficiency and can be efficient beyond even ~90%. This however, is yet a dream and not realized so far in any practical solar cell fabricated. Attempts are therefore made to improve the photovoltaic cells using different concepts. In this project attempt is to investigate the effect of different shapes and sizes of the gold/silver nanoparticles on trapping the light since efficient trapping of light is needed to increase the cell efficiency. Gold and silver nanoparticles exhibit absorption of electromagnetic radiation in the visible part of the electromagnetic spectrum known as Localized Surface Plasmon Resonance (LSPR). The use of anisotropic nanoparticles like rods, tetrapods, triangles, stars, cubes etc. have size and shape dependent much broader absorption properties which can extend in the visible range to IR, the part of the solar spectrum which in most of the cases is not possible to use. One can also make alloy plasmonic structures which also can affect the absorption favourably to improve the performance. In this project, nanoparticles of spherical, rod, stars, cubes and cage shapes of gold and silver were synthesized and their characterization was performed using UV-Visible spectrophotometer and FESEM. Then they are introduced into the widely used conductive polymer PEDOT:PSS (Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)) and their optical and electrical properties in solution and thin film are studied for measuring their light trapping efficiency