First-principles GW calculations for fullerenes, porphyrins, phtalocyanine, and other molecules of interest for organic photovoltaic applications

We evaluate the performances of ab initio $mathit{GW}$ 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 ${mathrm{C}}_{60}$ fullerene, pentacene, free-base porphyrins and phtalocyanine, PTCDA, and standard monomers such as thiophene, fluorene, benzothiazole, or thiadiazole. Standard $G$${}_{0}$$W$${}_{0}$ 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 $mathit{GW}$ with explicit treatment of the dynamical screening through contour deformation techniques.