Correlation between structural, morphological, and optical properties of spin-coated Poly (2,5-di(hexyloxy) cyanoterephthalylidene) (CN-PPV) thin films

Conjugated polymers (CPs) play a major role in optical applications due to their unique properties. In this current work, fluorine-doped tin oxide (FTO) and quartz substrates were coated with thin layers of poly (2, 5-di-hexyloxy) cyanoterephthalylidene (CN-PPV) by spin coating technique. X-ray Diffraction (XRD) was revealed the amorphous nature of CN-PPV/FTO and CN-PPV/quartz thin films. Atomic force microscopy (AFM) was used to examine surface grain form and size distributions for CN-PPV/FTO and CN-PPV/quartz thin films. Samples were exhibited similar functional groups, as determined by Fourier-transform infrared spectroscopy (FT–IR). UV–Vis-NIR spectroscopy was revealed a noticeable impact of the substrate on the optical gap, optical constants, and dielectric characterizations of the films. The third-order nonlinear susceptibility χ^{(3 )}, nonlinear refractive index, n⁽²⁾, of CN-PPV thin films, were valued in the wavelength range of 200–2500 nm by semi-empirical calculation. Finally, the nonlinear absorption coefficient (βc) was obtained using a semi-empirical approach. Such variations in optical characteristics are coupled with changes in structure and morphology, which are strongly related to the type of substrate. These findings will be open the way for the creation of nonlinear optical (NLO) thin films with enhanced performance for optoelectronic and photonic devices.