Annealing effect on the morphology, linear and non-linear optical properties of squaraine derivative thin films for optoelectronics applications

Abstract

Squaraine is a class of organic compounds that possess unique optical properties, including strong absorption of light, high fluorescence quantum yields, etc. Here, we explore the structural and spectroscopic investigations of 2,4-Bis[4-(N,N-dibenzylamino)-2,6 dihydroxyphenyl] squaraine dye (SQ) under different conditions of thermal effects. The molar absorptivity (εmolar) spectra were used to describe the electric dipole strength (q2) and the oscillator strengths (f) of SQ dye. The Surface morphology of SQ dye was investigated by AFM and the average roughness shows dependence on the annealing effect. A slight change in the optical energy gap (⁓ 0.3 eV) after annealing up to 473 K reflects the optical stability of our investigated thin films. The optical band transitions and photoluminescence (PL) emission spectra were described before and after annealing at 423 & 473 K. As the temperature annealing film increased to 473 K, the nonlinear parameters such as χ(3) and n2 decreased by about 44% and 36%, respectively. The good thermal stability, suitable optical band gap, and refractive index offer potential applications as active photonic materials in photonic/optoelectronic applications.