%0 Journal Article
%T Solar Cells Efficiency Increase Using Thin Metal Island Films
%A Alexander Axelevitch
%A Gady Golan
%J Journal of Solar Energy
%D 2013
%I 
%R 10.1155/2013/478219
%X Metal nanodimension structures have multiple applications in modern technology. Noncontinuous thin island metal films of several types of metals deposited on dielectric or semiconductor surface introduce a unique behavior. In response to light exposure in certain range, the metal islands present a resonant absorption of light accompanied with a collective behavior of free electrons in these islands. In this paper, we present one of the possible ways to increase the efficiency of solar cells with metal islands imbedded in a semiconductor junction. Rough calculation was performed for a silicon solar cell and showed an increase of 17.5% in the overall efficiency of the cell. 1. Introduction Solar cells, as alternative energy sources, attract much attention in recent decades due to enormous energy obtained by earth from the sun, about 1.2 ¡Á 1017£¿W. Solar cells have the potential to replace fossil fuels as the main means of electric power generation. However, solar cells of all types suffer from two main deficiencies: relatively low conversion efficiency and high cost in comparison with conventional fossil fuel electric sources. The search of ways to reduce fabrication costs and increase efficiency of photovoltaic devices is the main goal of researchers and developers. Unfortunately, efficiency of solar cells based on semiconductor materials is limited due to high electrical and optical losses [1]. Moreover, the luminescence (radiative) recombination further restricts the possible efficiency; thus, the efficiency of silicon solar cells cannot theoretically exceed 31% [2]. There are several ways to increase efficiency of solar cells. The first one consists in combining semiconductor photovoltaic converters with suitable heat absorbing bodies that is, water or oil for heat them and use this thermal energy. This specific method is already applied in industry. However, this method requires additional capital investments and significant complication of used equipment. The second method to improve efficiency is based on utilizing various semiconductor materials in order to enlarge the spectral efficiency. Multijunction devices, or heterojunction devices, can reach larger spectral efficiency by capturing different parts of the solar spectrum. A multi-junction device is a stack of individual single-junction cells in descending order of bandgaps. The top cell captures the high-energy photons and passes the rest of the photons on to be absorbed by lower-bandgap cells. Sze has shown [3] that consecutive combination of 36 junctions may attain an ideal efficiency of 72%.
%U http://www.hindawi.com/journals/jse/2013/478219/