Optical spectra and exchange-correlation effects in molecular crystals

摘要: We report the first-principles $GW$-Bethe--Salpeter equation and quantum Monte Carlo calculations of optical electronic properties molecular crystalline rubrene $({\mathrm{C}}_{42}{\mathrm{H}}_{28})$. Many-body effects dominate spectrum quasiparticle gap crystals. interpret observed yellow-green photoluminescence in microcrystals as a result formation intermolecular, charge-transfer, spin-singlet excitons. In contrast, spin-triplet excitons are localized intramolecular with predicted phosphorescence at red end spectrum. find that exchange energy plays fundamental role raising above intermolecular ones. Exciton binding energies to be around $0.5\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ (spin singlet) $1\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ triplet). The calculated is $2.8\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. theoretical absorption agrees very well recent ellipsometry data.