Luminescence and absorption analysis of undoped organic materials

Abstract

The authors model and analyze the electroluminescence and absorption properties of organic semiconductors using Al q3 as example. Instead of using a typical quasiparticle approach based on singlet and triplet excitons, they obtain the absorption and electroluminescence spectra by solving the equation of motion for the linear microscopic polarization in a hierarchical many-body framework. A special focus is put on Coulomb effects. The electronic structure input parameters for this model are obtained by molecular orbital calculations. In particular for Al q3, they find a (Coulomb) exciton binding energy of about 0.9 eV and discuss the impact of the strong carrier density induced Coulomb exchange shift on electroluminescence and absorption spectra. © 2007 American Institute of Physics.