Modelling the optical constants of organic thin films: impact of the choice of objective function

In this work, we model the optical constants of three organic materials usi ng a modified Lorentz oscillator model. We have analysed the impact of the choice of the objective or merit function, which is employed for model para meter estimation, on the modelling of the optical constants. The objective function for model parameter determination should be chosen in such a manne r that discrepancies between the experimental and calculated values for bot h parts of the index of refraction are minimized at the same time. We have found that the choice of objective function strongly influences the existen ce of multiple solutions. By combining a global optimization method, an app ropriately chosen objective Function and a modified oscillator model, we ob tain good agreement with the experimental data for three organic materials.