Annealing temperatures induced optical constant variations of methyl violet 2B thin films manufactured by the spin coating technique

► We report on the effect of annealing on structural and optical properties of MV2B. ► MV2B has an amorphous structure in its powder and as-deposited thin film forms. ► The absorption and refractive indices of MV2B are independent of film thickness. ► Indirect allowed transition has been observed in as-deposited film. ► Annealing reduces structural disorder and influences optical properties.