Solvent vapor annealing in the molecular regime drastically improves carrier transport in small-molecule thin-film transistors
AuthorsKhan, Hadayat Ullah
Payne, Marcia M.
Bhansali, Unnat Sampatraj
Smilgies, Detlef Matthias
Anthony, John Edward
KAUST DepartmentPhysical Sciences and Engineering (PSE) Division
Chemical and Biological Engineering Program
KAUST Solar Center (KSC)
Materials Science and Engineering Program
Organic Electronics and Photovoltaics Group
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AbstractWe demonstrate a new way to investigate and control the solvent vapor annealing of solution-cast organic semiconductor thin films. Solvent vapor annealing of spin-cast films of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-Pn) is investigated in situ using quartz crystal microbalance with dissipation (QCM-D) capability, allowing us to monitor both solvent mass uptake and changes in the mechanical rigidity of the film. Using time-resolved grazing incidence wide angle X-ray scattering (GIWAXS) and complementary static atomic force microscopy (AFM), we demonstrate that solvent vapor annealing in the molecular regime can cause significant performance improvements in organic thin film transistors (OTFTs), whereas allowing the solvent to percolate and form a liquid phase results in catastrophic reorganization and dewetting of the film, making the process counterproductive. Using these lessons we devise processing conditions which prevent percolation of the adsorbed solvent vapor molecules for extended periods, thus extending the benefits of solvent vapor annealing and improving carrier mobility by nearly two orders of magnitude. Ultimately, it is demonstrated that QCM-D is a very powerful sensor of the state of the adsorbed solvent as well as the thin film, thus making it suitable for process development as well as in-line process monitoring both in laboratory and in future manufacturing settings. © 2013 American Chemical Society.
SponsorsPart of this work was supported by KAUST's Office of Competitive Research Funds under Award FIC/2010/04. The authors acknowledge use of the D1 beamline at the Cornell High Energy Synchrotron Source supported by the National Science Foundation (NSF DMR-0936384) and NIH-NIGMS.
PublisherAmerican Chemical Society
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