Structural, optical, and photodetection characteristics of thermally evaporated Azure A chloride/FTO thin films

Thermally evaporated Azure A chloride thin films were deposited on fluorine-doped tin oxide (FTO) substrates with thicknesses ranging from 75 to 175 nm, and their structural, optical, and optoelectronic properties were systematically investigated. X-ray diffraction analysis indicates that the deposited films exhibit an amorphous structure, while optical measurements reveal strong absorption in the visible region with absorption coefficients on the order of 10⁴-10⁵ cm^-1. The optical bandgap shows a clear thickness dependence, with the lower-energy transition increasing from 1.27 to 1.57 eV and the higher-energy transition decreasing from 3.5 to 2.8 eV as the film thickness increases. Dispersion analysis reveals thickness-dependent refractive index and dielectric response, reflecting enhanced photon-matter interactions in thicker films. The optical conductivity and related parameters further confirm the influence of film thickness on charge carrier excitation under optical illumination. In addition, A simple Au/Azure A chloride/FTO device was fabricated to demonstrate the photoresponse behavior of the films under illumination. These results highlight the suitability of Azure A chloride thin films for optical and photonic applications.