title: Measurement of Small Molecular Dopant F4TCNQ and C60F36 Diffusion in Organic Bilayer Architectures.
abstract: The diffusion of molecules through and between organic layers is a serious stability concern in organic electronic devices. In this work, the temperature-dependent diffusion of molecular dopants through small molecule hole transport layers is observed. Specifically we investigate bilayer stacks of small molecules used for hole transport (MeO-TPD) and p-type dopants (F4TCNQ and C60F36) used in hole injection layers for organic light emitting diodes and hole collection electrodes for organic photovoltaics. With the use of absorbance spectroscopy, photoluminescence spectroscopy, neutron reflectometry, and near-edge X-ray absorption fine structure spectroscopy, we are able to obtain a comprehensive picture of the diffusion of fluorinated small molecules through MeO-TPD layers. F4TCNQ spontaneously diffuses into the MeO-TPD material even at room temperature, while C60F36, a much bulkier molecule, is shown to have a substantially higher morphological stability. This study highlights that the differences in size/geometry and thermal properties of small molecular dopants can have a significant impact on their diffusion in organic device architectures.
authors.affiliation: Department of Chemical Engineering and Materials Science, University of California , Davis, California 95616, United States.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Chemical Engineering and Materials Science, University of California , Davis, California 95616, United States.
authors.forename: Chris W
authors.initials: CW
authors.lastname: Rochester
authors.affiliation: Department of Chemical Engineering and Materials Science, University of California , Davis, California 95616, United States.
authors.forename: Ian E
authors.initials: IE
authors.lastname: Jacobs
authors.affiliation: Lawrence Livermore National Laboratory , Livermore, California 94550, United States.
authors.forename: Stephan
authors.initials: S
authors.lastname: Friedrich
authors.affiliation: Department of Chemical Engineering and Materials Science, University of California , Davis, California 95616, United States.
authors.forename: Pieter
authors.initials: P
authors.lastname: Stroeve
authors.affiliation: Department of Physics, Oxford University , Oxford OX1 3PU, United Kingdom.
authors.forename: Moritz
authors.initials: M
authors.lastname: Riede
authors.affiliation: Department of Chemical Engineering and Materials Science, University of California , Davis, California 95616, United States.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Moulé
keywords: device stability; diffusion; dopant; organic light emitting diodes; organic photovoltaics