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dc.contributor.authorVan den Brande, Niko
dc.contributor.authorGujral, Ankit
dc.contributor.authorHuang, Chengbin
dc.contributor.authorBagchi, Kushal
dc.contributor.authorHofstetter, Heike
dc.contributor.authorYu, Lian
dc.contributor.authorEdiger, Mark D.
dc.date.accessioned2019-03-28T20:17:40Z
dc.date.available2019-03-28T20:17:40Z
dc.date.issued2018-08-28
dc.identifier.urihttp://digital.library.wisc.edu/1793/79052
dc.descriptionSynopsis: Anisotropic CBP glasses were prepared by vapor deposition. After eliminating crystal growth at the free surface, these glasses crystallized into either the α or γ polymorph, depending on glass structure. Crystals of both polymorphs grew rapidly below the glass transition temperature Tg compared to previously studied systems. Tg was found to be about 385 K, well above previously reported values.en_US
dc.description.abstractGlasses of a common OLED host material, 4,4′-bis(N-carbazolyl)-1,1′-biphenyl or CBP, were prepared by vapor deposition at various substrate temperatures. Consistent with previous work, the substrate temperature during deposition controls the anisotropic structure of the glass. Crystal growth at the free surface of CBP was very fast and was eliminated by covering the free surface with a thin overlayer of vapor-deposited tris(8-hydroxyquinoline) aluminum (Alq3). It was observed that vapor-deposited glasses of CBP with an overlayer crystallized into either the α or γ polymorph, depending on the glass structure. To the best of our knowledge, this is the first demonstration that two glasses of the same organic compound, subjected to the same annealing conditions, grow crystals of different polymorphs. The α polymorph exhibited a fine-grained morphology, reminiscent of previous studies on glass-crystal (GC) growth, while the γ polymorph exhibited dendritic growth. Crystals of both polymorphs grew rapidly below the glass transition temperature Tg in comparison to previously studied GC growth systems such as o-terphenyl. Surprisingly, Tg for CBP was found to be about 385 K, well above previously reported values.en_US
dc.description.sponsorshipFellowship of the Belgian American Educational Foundation U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, Award DE-SC0002161 National Science Foundation University of Wisconsin Materials Research Science and Engineering Center (DMR-1720415) NIH 1S10 OD020022-1 Paul J. and Margaret M. Benderen_US
dc.language.isoenen_US
dc.publisherAmerican Chemical Societyen_US
dc.titleGlass Structure Controls Crystal Polymorph Selection in Vapor-Deposited Films of 4,4′-Bis(N-carbazolyl)-1,1′-biphenylen_US
dc.typeArticleen_US
dc.identifier.doi10.1021/acs.cgd.8b00329


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