Excitons and Davydov splitting in sexithiophene from first-principles many-body Green’s function theory

摘要: Organic semiconductors have promising and broad applications in optoelectronics. Understanding their electronic excited states is important to help us control spectroscopic properties performance of devices. There been a large amount experimental investigations on spectroscopies organic semiconductors, but theoretical calculation from first principles this respect still limited. Here, we use density functional theory (DFT) many-body Green’s function theory, which includes the GW method Bethe-Salpeter equation, study excited-state one prototypical semiconductor, sexithiophene. The exciton energies sexithiophene both gas bulk crystalline phases are very sensitive exchange-correlation functionals used DFT for ground-state structure relaxation. We investigated influence dynamical screening electron-hole interaction energies, found be pronounced triplet excitons has taken into account calculations. In single crystal, energy lowest close half singlet one. While lower-energy intramolecular Frenkel excitons, higher-energy intermolecular charge-transfer type. calculated optical absorption spectra Davydov splitting good agreement with experiments.