Gamma radiation induced variation in structure formation and optical characteristics of evaporated tris [2-phenylpyridinato-C₂,N]iridium(III) films prepared by electron beam evaporator in photovoltaic applications

Abstract This study fabricates novel tris (2-phenylpyridinato-C2, N] iridium III I r ( p p y ) 3 thin films using an electron beam evaporator and investigates their structure formation, surface morphology, and linear/nonlinear optical properties. The structural features of I r ( p p y ) 3 thin films were examined using Fourier Transform spectroscopy (FTIR), x-ray diffraction (XRD), Scanning Electron Microscope (SEM). The optical c.characteristics for various doses of gamma radiation (3 kGy, 6 kGy and 9kGy) were investigated using a UV-Vis-NIR spectrophotometer in the wavelength range from 200 nm to 2500 nm. In addition, the values of fundamental energy gap (Efundamental) values showed a reduction from 2.30 to 1.92 eV and urbach energy ( E U ) increasing from 0.23 to 0.30 when the deposited film irradiated for 9 kGy. The third-order nonlinear susceptibility ( χ ( 3 ) ), the nonlinear absorption coefficient ( β ) and the nonlinear refractive index ( n 2 ) were determined for all gamma doses. Furthermore, The optical electronegativity ( η o p t ), the first moment ( M − 1 ), the second moments of optical spectra ( M − 3 ), the oscillator strength (f), the dispersion energy ( E d ), infinite dielectric constant ( ε ∞ ), oscillator energy,oscillator energy ( E 0 ), the lattice dielectric constant ( ε L ), and to the effective mass N m * for as deposited film are calculated as : 1.860, 17.29, 300.20, 0.9960 (eV)2, 4.15 eV, 4.52, 1.18 eV, 5.58, and 8.86 × 1059 kg−1 m−3 respectively. The high values of ( χ ( 3 ) ) for as deposited and irradiated are essential for the creation of low power devices for nonlinear optical applications involving ultrafast switches, optical computers, and ultra-pulsed lasers.</jats:p