Optical properties of some synthesized azo thin films

► Thermal evaporation process does not affect the chemical structure of ligands. ► Thermally deposited PATT-Ln thin film can be considered as completely amorphous. ► The optical absorption showed many absorption bands. ► The type of optical transition is found to be direct allowed transition. ► The Eg values are in the range 1.78-2.29 eV according to p-(NO2 > Cl > H > OCH3 > CH3).