Exploring the molecular spectroscopic and electronic characterization of nanocrystalline Metal-free phthalocyanine: a DFT investigation

Abstract

The molecular structure optimization and harmonic vibrational frequencies of nanocrystalline metal-free phthalocyanine were investigated using the density functional theory (DFT) implemented in the Gaussian 09 program through B3LYP/6-311G basis set. Thermodynamic and non-linear optical (NLO) characteristics, total dipole moment, HOMO–LUMO energies, natural population analysis (NPA), and global chemical reactivity descriptors were examined. TD-DFT evaluations were used to interpret the electronic absorption. The experimental results and computed values match up adequately. An essential component of photovoltaic devices and the optimized HOMO–LUMO energy gap (2.16 eV) were estimated and compared with those obtained experimentally. The energy band model was used to check the probability of the transition type and estimate the values of energy gaps, which were found to be indirectly allowed. To provide a comprehensive picture for the characterization and determine the activation energy of the charge carriers, the DC electrical conductivity was also examined. It was revealed to have a value between 0.767 and 1.288 eV depending on the temperature range.

Using Recycled Tetrapak and Doped Titanyl/Vanadyl Phthalocyanine to Make Solid-State Devices

“…The first portion of the Tauc plots can be referred to the energy onset gap and is defined as the formation of a bound electron-hole pair in the semiconductor's materials, or Frenkel exciton [50,57]. The second portion could be attributed to the fundamental energy band gap between the HOMO and the LUMO [50,57]. The obtained values of these band gaps corroborated the calculated theoretical value.…”

“…The Tauc method was used to calculate the direct and indirect energy band gap values from the UV-Vis spectra. The energy band gap (Eg) was obtained by analyzing the variation of the absorption coefficient (α) with the photon energy (hν) in the high absorption region as follows [50,57]: The Tauc method was used to calculate the direct and indirect energy band gap values from the UV-Vis spectra. The energy band gap (Eg) was obtained by analyzing the variation of the absorption coefficient (α) with the photon energy (hν) in the high absorption region as follows [50,57]:…”

“…where A is a constant and m is an exponent parameter that depends on the type of transition [50,57], m = 1/2 for indirect and m = 2 for direct forbidden electronic transitions. The relation between (αhν) m vs. hν was plotted in Figure 6b,c to extract the values of the E g by extrapolating the straight line portion.…”

“…These figures and Table 2 present the values of the fundamental and the onset gaps for indirect and direct electronic transitions. The first portion of the Tauc plots can be referred to the energy onset gap and is defined as the formation of a bound electron-hole pair in the semiconductor's materials, or Frenkel exciton [50,57]. The second portion could be attributed to the fundamental energy band gap between the HOMO and the LUMO [50,57].…”

Impact of the thickness of phthalocyanine films and its metal complexes on optical and electrical properties

“…Phthalocyanines are large aromatic organic compounds constructed from four isoindole units connected by nitrogen atoms. Phthalocyanines are chemically and thermally stable, most of them are organic p-type semiconductors and have photoconductivity, easily forming ordered thin films [1,2]. This determines their use as media for optical recording of information, for the manufacture of light-emitting diodes (LEDs), solar cells, gas sensors, high-speed magnetic field sensors [3][4][5].…”