Simulació de cel·les fotovoltaiques orgàniques

Abstract

In this work we have simulated an organic solar cell formed by an acceptor molecule (PC71BM and a donor molecule (p-DTS (FBTTh2)2, one of the organic systems with the best performance, through a force field based on the parameters of the GAFF (generalized Amber force field) to verify the viability of the parameters by default and the approximations used. These approaches have been made regarding the silicon atom present in the donor molecule, which has no parameter in the GAFF and the corresponding ones have been used for a carbon atom sp3 in the binding terms and the silicon ones in non-binding terms. Both molecules maintain the connectivity and behave normally during molecular dynamics, so the approximations used are applicable in this case and serve as an approximation to the real silicon parameters. Once this approach has been checked, the objective is to improve the parameters existing in the GAFF, in particular the parameters that describe the torsion of the links around the rings of the donor molecule, using a genetic algorithm. This method consists in a random generation of new results that simulates the functioning of a population of individuals based on chromosome-like mechanisms, such as cross-linking and random mutations. More specifically, a method called the roulette wheel selection has been used, which gives priority to the results that are closer to the objective and allows them to participate more in the reproduction of these generations of results. As a reference energies to improve the parameters of the GAFF it has been used a profile calculated using quantum mechanics and the resolution of the Schrödinger equation using the density functional theory. The implementation of the parameters obtained through this method within the force field has improved the results regarding to the ones calculated without the contribution of the torsion energy between the rings