Electronic and optical properties of families of polycyclic aromatic hydrocarbons: A systematic (time-dependent) density functional theory study

By Giuliano Malloci, Giancarlo Cappellini, Giacomo Mulas, Alessandro Mattoni. 2011

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Abstract Homologous classes of polycyclic aromatic hydrocarbons (PAHs) in their crystalline state are among the most promising materials for organic opto-electronics. Following previous works on oligoacenes we present a systematic comparative study of the electronic, optical, and transport properties of oligoacenes, phenacenes, circumacenes, and oligorylenes. Using density functional theory (DFT) and time-dependent DFT we computed: (i) electron affinities and first ionization energies; (ii) quasiparticle correction to the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap; (iii) molecular reorganization energies and (iv) electronic absorption spectra of neutral and ±1 charged systems. The excitonic effects are estimated by comparing the optical gap and the quasiparticle corrected HOMO–LUMO energy gap. For each molecular property computed, general trends as a function of molecular size and charge state are discussed. Overall, we find that circumacenes have the best transport properties, displaying a steeper decrease of the molecular reorganization energy at increasing sizes, while oligorylenes are much more efficient in absorbing low-energy photons in comparison to the other classes.

Subfields: Electrical and Electronic Engineering, Organic Chemistry

View Paper: https://www.semanticscholar.org/paper/7277ee3fc6a8d9d800be65d392e66ad0ed79a08e