Monte Carlo Simulations of Charge Transport in Polymers for Second Order Nonlinear Optics

Abstract

In order to obtain sufficient noncentrosymmetric Chromophore orientation to achieve second order nonlinear properties in a molecularly doped polymer, a very strong field must be applied during poling. The resultant charge transfer induced by the strong field behaves very differently from currents found in semiconductors or metals. A Monte Carlo simulation has been developed to model charge carriers moving through a poled polymer single layer film. The program consists of a lattice containing 36,000 hopping sites with a Gaussian distribution of site energies. The hopping behavior can be manipulated by changing input variables including the temperature, magnitude of the applied field, concentration of the chromophores, overlap parameter, and the Gaussian width of the distribution of site energies. We have also developed a simulation based a random distribution of sites instead of the lattice configuration, and are currently examining the relationship between energetic and positional disorder. We have constructed a preliminary charge transport model which can predict current as a function of the inputs, positional disorder and energetic disorder. Thus far, models available in the literature consider only charge migration in lattice based, semi-infinite crystals, which are not suitable for polymeric materials.