Optical properties change with the addition and diffusion of Bi to As2S3 in the Bi/As2S3 bilayer thin film

► The article reports the optical properties change due to Bi layer on As2S3 thin film. ► The reduction of Eg is due to the creation of localized states in the band gap. ► Photo bleaching is observed in the Bi/As2S3 bilayer film upon light illumination. ► New bonds are formed due to photo diffusion of Bi into As2S3 matrix.