Thickness dependent optical dispersion and nonlinear optical properties of nanocrystalline fluorescein dye thin films for optoelectronic applications

In the current work, the authors have fabricated the good quality nanocrystalline thin films of Fluorescein dye with different thicknesses (i.e. 145, 175 and 210 nm) using cost effective spin coating technique for the first time. Structural examination was done by X-ray diffraction. Surface morphology was assessed by atomic force microscopy which verified that the fabricated thin films are of high quality with nanostructure morphology. UV-vis-NIR transmittance and reflectance spectra were recorded and various optical parameters were calculated. The enhancement in the values of optical band gap, refractive index, optical dielectric constant was observed with thickness. The nonlinear optical constants such as:X¹,X³and n₂ were also enhanced with increasing the thicknesses of the films and found to be in the range of 1.88-2.25, 0.15-0.32 esu and 1.0 × 10^-13 to 1.8 × 10^-12 esu. All the results suggest that it may be useful in optoelectronic applications.