Spectrophotometric calculations of optical linearity and nonlinearity of nanostructured Pyronin Y/FTO optical system for optoelectronic applications

Abstract

Pyronin Y (PY) is an organic dye with semiconducting behavior which can be ascribed as a novel dye in different aspects of material science and device engineering. Thin films of Pyronin Y were prepared using a low-cost spin coating method deposited on FTO substrate. XRD showed that PY thin film has an amorphous structure with crystalline peaks corresponding only to FTO layer/glass. Transmittance, reflectance, and absorbance are measured for Pyronin Y/FTO of thickness around 200nm at the normal incident light in the wavelength range 300–2500nm. PY has an absorption valley in the visible region. Based on the measured transmittance and reflectance, the refractive index n of PY/FTO is calculated by using the Fresnel’s equations. Dielectric constants, dissipation factor, band gap and optical/electrical conductivity were also determined and analyzed. Plotting of (αhν)1/2 versus the incident photon energy is giving the values of the band gap. Three optical band gaps are found, the highest one is designed for FTO layer/glass and equals 3.569eV and the other two band gaps are (1.955 and 1.356eV) for Pyronin Y/FTO film. For PY films on FTO, the value of band gap (1.955eV) is described the fundamental band gap and the second band gap (1.356eV) is described as the trap energy inside the fundamental band gap. The nonlinear optical properties including the third order nonlinear optical susceptibility and nonlinear refractive index of PY/FTO glass were calculated and analyzed by using spectrophotometric data. Hence, Pyronin Y/FTO with a graded band gap have a unique optical constant that useful in multi-device applications for physics and engineering.