The effect of solvent on the optical properties of cyanine dye films

In this paper, several cyanine dyes in different solvents were spin-coated onto glass substrates to form thin films. Vis-NIR spectra of reflection of the films were measured and optical constants (complex refraction index) were calculated. It was found the solvents could greatly affect the optical properties of dye films. Atomic force microscopy (AFM) was applied to observe the morphologies of the film surfaces and the results demonstrated that the reflectivity was closely related to the surface roughness of film. High surface roughness has a strong scattering effect on light and will lower the reflectivity. When tetrafluoro-propanol and chloroform were employed as solvents, the surface roughness of the film was low and high reflectivity was reliably obtained.