Simulação do limiar de percolação elétrico de células orgânicas de polímero/nanotubos de carbono para aplicação em células fotovoltáicas

Abstract

In the extent of new technologies for the use of renewable energy, photovoltaic systems are in increasing application. Thus, new materials have been explored and research has been done to advance photovoltaic technology. The latest representative of this technology are the organic cells, which are in the research and development, testing and small-scale production phase, yet have shown semiconductor potential, resulting in the responsibility of acting on light absorption, generation, separation and transport of charges. A portion of these devices are produced by mixing a conductive polymer and a fullerene derivative, mainly at the nanometer scale. Carbon nanotube conductive polymer nanocomposites have a high potential for this application where conductivity and low specific weight are required. However, the high cost of these loads impairs a thorough research of the process conditions and the study of electrical percolation, which is a decisive condition in the transformation of insulating polymer into semiconductor. In this scope, the modeling and simulation of this threshold play a very important role in the development of this field of study, besides propelling the idealization of this research, in which a study of the electrical percolation of nanocomposites made up of matrix-dispersed carbon nanotubes was performed. This research was simulated through a Monte Carlo program and supported by the excluded volume model for two - dimensional and three - dimensional matrix systems. The percolation threshold was analyzed for different aspect ratios, volume fractions and conductive load geometries. After the simulations, it was shown that the percolation threshold decreased as the aspect ratio increased.