Investigating the properties of nano crystalline beta metal-free phthalocyanine films: From molecules to optoelectronic applications

Abstract

A study was conducted to investigate the structural and optical properties of nanocrystalline beta metal-free phthalocyanine (β-H2Pc) thin films using computational and experimental methods. DFT calculations using the B3LYP basis set 6–311G were performed to predict the HOMO-LUMO gap of the β-H2Pc (2.13 eV). The crystalline structural properties of the β-H2Pc were examined through XRD analysis, which revealed that the powder β-H2Pc had a monoclinic polycrystalline structure, while the β-H2Pc thin film was amorphous. Various methods were used to determine and compare the average crystallite size and microstrain, with the size-strain plot method yielding an average crystallite size and microstrain size of 73.15 nm and 0.0051, respectively. Using SEM to analyze the film's surface topography, the mean grain size was found to be 0.85 µm due to agglomeration. Linear and nonlinear spectrophotometric measurements were employed to examine the optical properties of the β-H2Pc thin film. The film exhibited indirectly permitted inter-band transitions, with the onset and fundamental band gaps of 1.51 eV and 2.74 eV, respectively. Furthermore, several absorption and dispersion characteristics for thin films were identified. The properties exhibited by Au/β-H2Pc/p-Si/Al heterojunction indicate its potential suitability for photosensor applications.