title: The role of C-H and C-C stretching modes in the intrinsic non-radiative decay of triplet states in a Pt-containing conjugated phenylene ethynylene.
abstract: The intrinsic non-radiative decay (internal conversion) from the triplet excited state in phosphorescent dyes can be described by a multi-phonon emission process. Since non-radiative decay of triplet excitons can be a significant process in organic light-emitting diodes, a detailed understanding of this decay mechanism is important if the overall device efficiency is to be controlled. We compare a deuterated Pt(II)-containing phenylene ethynylene with its non-deuterated counterpart in order to investigate which phonon modes control to the non-radiative decay path. We observe that deuteration does not decrease the non-radiative decay rate. A Franck-Condon analysis of the phosphorescence spectra shows that the electronic excitation is coupled strongly to the breathing mode of the phenyl ring and the C≡C carbon stretching modes, while high-energy C-H or C-D stretching modes play an insignificant role. We, therefore, associate the internal conversion process with the carbon-carbon stretching vibrations.
authors.affiliation: Experimentalphysik II and Bayreuth Institute of Macromolecular Science, University of Bayreuth, 95440 Bayreuth, Germany. Anna.koehler@uni-bayreuth.de
authors.forename: Anna
authors.initials: A
authors.lastname: Köhler
authors.forename: Amena L T
authors.initials: AL
authors.lastname: Khan
authors.forename: Joanne S
authors.initials: JS
authors.lastname: Wilson
authors.forename: Carsten
authors.initials: C
authors.lastname: Dosche
authors.forename: Mohammed K
authors.initials: MK
authors.lastname: Al-Suti
authors.forename: Hakikulla H
authors.initials: HH
authors.lastname: Shah
authors.forename: Muhammad S
authors.initials: MS
authors.lastname: Khan