Physical and optoelectronic characteristics of novel low-cost synthesized coumarin dye-based metal-free thin films for light sensing applications

Herein, we have evolved a new and efficient procedure for the synthesis of 3-(2-(4-bromophenyl)hydrazone)-2,4-chromandione BPHC via the cyclization of (4-bromo-phenylhydrazono)-malonic acid with phenol in the presence of zinc chloride. The thermal stability of the final product is investigated by using DSC/TGA techniques. Thermal deposited BPHC thin films are successfully prepared under vacuum. The IR results of BPHC powder and thin films declare that the deposited films exhibit a stable molecular structure even upon annealing. The as-deposited BPHC thin films exhibit a polycrystalline phase and smooth surface, which are enhanced by annealing at 373 K as observed in the XRD and FE-SEM results. The spectrophotometric measurements showed the enhanced optical absorption in UV and visible spectral bands for the annealed films at 373 K with a decreased energy gap of about 2.37 eV. The dispersion behavior is analyzed as a function of annealing temperatures by using a single oscillator model. The BPHC thin films showed strong PL emission at 522 nm with excitonic binding energy similar to 0.17 eV. Furthermore, the organic/inorganic hetero-architecture based on BPHC/n-type silicon is designed and fabricated with significant rectification behavior. The microelectronic parameters of the manufactured heterojunction are calculated and discussed in detail. Moreover, the fabricated device showed a promising stable linear response to light signals with responsivity similar to 16.9 mA/W and specific detectivity similar to 3.35 x 10(10) Jones. The repeatable, stable, and efficient performance of the present device suggests this material as a powerful candidate for photosensing applications.