2008/02/21 by Na Sai, Murilo L. Tiago, James R. Chelikowsky +1
Chemistry · Engineering · Physics and Astronomy · #Molecular Junctions and Nanostructures #Photochemistry and Electron Transfer Studies #Spectroscopy and Quantum Chemical Studies #cond-mat.mtrl-sci
paper · pdf · doi:10.1103/physrevb.77.161306
published as Phys. Rev. B 77, 161306(R) (2008) · 4 pages, 4 figures
arxiv created 2008/02/21 · openalex publication_date 2008/04/30 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We report the first-principles GW-Bethe--Salpeter equation and quantum Monte Carlo calculations of the optical and electronic properties of molecular and crystalline rubrene (C42H28). Many-body effects dominate the optical spectrum and quasiparticle gap of molecular crystals. We interpret the observed yellow-green photoluminescence in rubrene microcrystals as a result of the formation of intermolecular, charge-transfer, spin-singlet excitons. In contrast, spin-triplet excitons are localized and intramolecular with a predicted phosphorescence at the red end of the optical spectrum. We find that the exchange energy plays a fundamental role in raising the energy of intramolecular spin-singlet excitons above the intermolecular ones. Exciton binding energies are predicted to be around 0.5\phantom\rule0.3em0exeV (spin singlet) to 1\phantom\rule0.3em0exeV (spin triplet). The calculated electronic gap is 2.8\phantom\rule0.3em0exeV. The theoretical absorption spectrum agrees very well with recent ellipsometry data.