Investigation of Structural, Optical, Dielectric, and Third-Order Nonlinear Optical Properties of Benzotriazole Picrate Single Crystal for Optoelectronic Applications

Organic nonlinear optical (NLO) crystals are widely acknowledged to be an important material in optoelectronics applications due to their molecular nature, in which the molecular structure can be modified through synthetic reactions, leading to improved NLO properties. Picric acid and 1,2,3-benzotriazole (BTP) were used as solvents in methanol to grow BTP crystals using the slow evaporation technique in an ambient environment. Based on structural studies, it was determined that the as-grown crystal had a monoclinic structure and the functional groups were confirmed through spectroscopical analysis. The optical properties of the BTP crystal were investigated using optical spectroscopy analysis in the wavelength range of 200–1200 nm, and its peak wavelength was determined to be at 310 nm. The as-grown BTP crystals display low dielectric loss based on dielectric analysis. Thermogravimetric and Differential Thermal Analysis (TG-DTA) were performed to examine phase transitions and temperature stability of the compound. The positive photoconductivity properties of the crystal were confirmed by photoconductivity measurements. The microhardness test was carried out to assess the mechanical strength of the BTP crystal. Third-order NLO characteristics, including nonlinear index of refraction (n2), two-photon absorbency coefficient (β), and third-order NLO susceptibility (χ3), were estimated using the Z-scan characterization technique.