Optical characterizations of thermally evaporated perylene-66 (dye content 40%) thin films

The effect of annealing temperatures on the optical properties of perylene-66 (Dye content 40%) thin films has been reported. The optical constants (refractive index, n, and absorption index, k) of the as-deposited and annealed films have been obtained in the wavelength range 200–2500 nm by using spectrophotometric measurements at nearly normal incidence. The obtained optical constants were used to estimate the type of transition for the as-deposited and annealed films. The single oscillator model and Drude model of free carriers' absorption have been used for the analysis of refractive index dispersion, in a low frequency range, before and after annealing.

► Optical properties of thermally evaporated perylene-66 thin films have been investigated.
► Absorption edge can be interpreted by considering the existence of two indirect optical transitions.
► Refractive index of the as deposited film decreases with annealing.