Optical studies of Rhodamine B doped polymethyl methacrylate (PMMA) films

Abstract

In this paper the influence of fluorescent dye doping on the optical properties of polymethylmethacrylate (PMMA), in particular on the optical band gap and refractive index of PMMA host matrix is reported. Solution casting method was used to prepare the films of pure PMMA and rhodamine-B doped PMMA films containing varying levels of doping and their optical properties were evaluated. UV–Visible spectra were used to evaluate the optical parameters; uv-absorption spectra reveal absorption bands between 262 and 284 nm for pure PMMA. However, dye doped PMMA film showed absorption bands in the range between 262 and 560 nm depending upon the degree of doping of dye into the film. Optical absorption measurements showed strong modifications in optical properties as a result of doping dye guest molecules into the host PMMA matrix system. It is observed that all optical parameters such as absorption band, absorption edge, energy band gap (direct and indirect) got affected by doping of the dye. Indirect optical band gap of pure PMMA was observed as 4.72 eV but it reduced to 4.13 eV on incorporation of rhodamine-B into PMMA matrix. Studies on the metallization criterion (M) implicate better scope of electronic mobility with the increase in the dopant concentration into the film.