Optical properties of PVT grown bromoaluminium phthalocyanine nanostructures using UV–visible–NIR spectroscopy

In this paper, we have studied the optical properties of bromoaluminium phthalocyanine (BrAlPc) nanostructures prepared by physical vapor phase transport (PVT) using UV–visible–NIR spectroscopy. Field emission scanning electron microscopy (FESEM) images show that different nanostructures namely nanocorals, nanorods and nanothistles have been obtained at varied source-substrate distances. By analyzing the spectrophotometric measurements of the absorbance, transmittance and reflectance spectra in the range of 300–2500 nm the optical characteristics, such as the optical absorption, Urbach energy, extinction coefficient, refractive index, and dielectric characteristics as a function of incident photon energy have been evaluated. We have found that the values of fundamental optical band gap and the energy of trap levels of all nanostructures have no remarkable changes. It is seen that the Urbach energy of BrAlPc nanorods is higher than nanocorals and nanothistles indicating higher structural disorder. Moreover, the occurrence of doublet in the Q-band region reveals that the BrAlPc nanocorals and nanorods are in $\alpha$-phase while the BrAlPc nanothistles is in $\beta$-phase. Moreover, different dispersion and absorption parameters have been estimated for different BrAlPc nanostructures. The obtained optical results for novel grown BrAlPc by PVT method may be of interest for practical applications.