Abstract
We evaluate the performances of ab initio calculations for the ionization energies and highest occupied molecular orbital-lowest unoccupied molecular orbital gaps of 13 gas phase molecules of interest for organic electronic and photovoltaic applications, including the fullerene, pentacene, free-base porphyrins and phtalocyanine, PTCDA, and standard monomers such as thiophene, fluorene, benzothiazole, or thiadiazole. Standard calculations, that is, starting from eigenstates obtained with local or semilocal functionals, significantly improve the ionization energy and band gap as compared to density functional theory Kohn-Sham results, but the calculated quasiparticle values remain too small as a result of overscreening. Starting from Hartree-Fock-like eigenvalues provides much better results and is equivalent to performing self-consistency on the eigenvalues, with a resulting accuracy of 2%–4 as compared to experiment. Our calculations are based on an efficient Gaussian-basis implementation of with explicit treatment of the dynamical screening through contour deformation techniques.
- Received 17 November 2010
DOI:https://doi.org/10.1103/PhysRevB.83.115103
©2011 American Physical Society