Electron binding energies using perturbative delta-SCF method

~~~~~ The knowledge of fundamental and optical gaps is of significant importance for organic photovoltaics. The electron binding~energies estimated from the Kohn-Sham eigenvalues are significantly underestimated. Here, we use our recently outlined perturbative delta-SCF approach to compute the electron binding energies of a number of aromatic organic molecules commonly used in organic photovoltaics. Further, the electron affinities are also computed for the C60, C70 and PCBM. The results show~that the perturbative delta-SCF provide adequate description of valence electron binding energies. We also applied the method to compute the core binding energies and the core-valence excited states.~ While the method can successfully~predict the core-valence excited states the results on the core-binding energies are mixed. The strategies for improvement of the core binding energies will be discussed. \newline