Spectral Effects of Microscopic and Mesoscopic Disorder in Organic Films -- Model Calculations

Effects of microscopic orientational disorder on electro-absorption of charge-transfer (CT) states in the high-temperature phase of the C₆₀ crystal are simulated on a cluster consisting of 108 molecules. The results suggest that this kind of disorder may be successfully modeled in terms of an effective crystal with full translational symmetry. Mesoscopic disorder is simulated for thin films of sexithiophene. The spectral broadening observed in absorption is attributed to the non-analyticity of the calculated dipole sums at k = 0, resulting in their dependence on crystallte orientation with respect to incident radiation.