Excitons in perylene tetracarboxdiimide crystals for optoelectronics

In this contribution, we present steady-state and timeresolved photoluminescence measurements, as well as absorbance measurements, on dilute solutions and on solution-grown crystals of a perylene tetracarboxdiimide derivative (EPPTC). We also present density functional theory (DFT) calculations of their electronic structure. These molecules self-assemble into highly anisotropic needle-shaped crystals with monoclinic structure, as revealed by X-ray diffraction techniques and polarized optical microscopy. We find experimentally that the Huang-Rhys factor for this molecule is 0.565, which is in good agreement with that extracted from ab initio calculations (0.678). We demonstrate that in a film, the nature of photoexcitations is a vibrationally dressed Frenkel exciton and that these recombine radiatively with a distribution of excited-state constants centered at ∼ 1 ns–1. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)