Gamma radiation-induced changes on the optical properties of dibenzthiopheno-perylene-N,N′-dicyclohexylimide thin films

•The effect of γ-irradiation on the optical properties of perylene-66 films has been reported.•From fundamental absorption edge, a picture of the energetic transitions of was described.•The γ-ray irradiation has an effect on the fundamental energy gap.•The molecular polarizability was used to describe the change in the refractive index.•A single-oscillator model and Drude model were used to describe the refractive index.

The effect of γ-irradiation (6 kGy) on the optical properties of thermally evaporated 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 γ-irradiated films have been obtained in the wavelength range 200–2500 nm using spectrophotometric measurements at nearly normal incidence. The obtained optical constants were used to estimate the type of transition for the as-deposited and irradiated films. The single oscillator model and Drude model of free carriers′ absorption were used for the analysis of refractive index dispersion, in the normal dispersion range, before and after γ-irradiation.