Spectroscopic and morphological investigation of conjugated photopolymerisable quinquethiophene liquid crystals

Handle URI:
http://hdl.handle.net/10754/564596
Title:
Spectroscopic and morphological investigation of conjugated photopolymerisable quinquethiophene liquid crystals
Authors:
McGlashon, Andrew J.; Zhang, Weimin; Smilgies, Detlef Matthias; Shkunov, Maxim N.; Genevičius, Kristijonas; Whitehead, Katherine S.; Amassian, Aram ( 0000-0002-5734-1194 ) ; Malliaras, George G.; Bradley, Donal D C; Heeney, Martin J.; Campbell, Alasdair J.
Abstract:
3′-methyl-(5,5′′-bis[3-ethyl-3-(6-phenyl-hexyloxymethyl) -oxetane])-2,2′:5′,2′′-terthiophene (5T(Me)Ox) is a solution processable small molecule semiconductor displaying smectic-C and nematic liquid crystal phases. The pendant oxetane group can be polymerized in situ in the presence of a suitable photoacid at concentrations ≥1% by weight. Spin-coated films of pure 5T(Me)Ox and 5T(Me)Ox doped with the soluble photoacid were characterized by absorption and photoluminescent spectroscopy. Thick pristine films showed absorption and emission from a crystalline phase. Thin monolayer (<5 nm) films, as well as thicker photoacid doped films, instead showed absorption from an H-aggregate phase and emission from an excimer. Optical microscopy showed a significant change in film structure upon addition of the photoacid; large and well-orientated crystals being replaced by much smaller domains which appear to vary in thickness. Grazing Incidence Wide Angle X-Ray Scattering (GIWAXS) was used to characterize the packing and orientation of molecules in the crystalline and doped samples. The results are consistent with the photoacid doped samples forming layers of H-aggregate phase monolayer sheets parallel to the substrate where the photoacid inhibits the transition into the three-dimensionally ordered crystalline phase. Field-effect transistors and light emitting diodes were constructed incorporating 5T(Me)Ox as the active layer. Pure 5T(Me)Ox field-effect transistors showed good, p-type device characteristics, but the morphological changes upon doping result in a loss of transistor action. In the diodes, curing through melting and exposure to UV light followed by photoacid removal resulted in an increase in current density but a decrease in light emission. These results indicate that the presence of the photoacid (≥1% by weight) can have a dramatic effect on the structure, morphology and device performance of ordered, photopatternable materials for organic electronics. © 2012 Elsevier Inc. All rights reserved.
KAUST Department:
Materials Science and Engineering Program; Physical Sciences and Engineering (PSE) Division; Solar and Photovoltaic Engineering Research Center (SPERC); Organic Electronics and Photovoltaics Group
Publisher:
Elsevier BV
Journal:
Current Applied Physics
Conference/Event name:
International Workshop on Flexible & Printable Electronics
Issue Date:
Sep-2012
DOI:
10.1016/j.cap.2011.07.042
Type:
Conference Paper
ISSN:
15671739
Appears in Collections:
Conference Papers; Physical Sciences and Engineering (PSE) Division; Materials Science and Engineering Program; Solar and Photovoltaic Engineering Research Center (SPERC)

Full metadata record

DC FieldValue Language
dc.contributor.authorMcGlashon, Andrew J.en
dc.contributor.authorZhang, Weiminen
dc.contributor.authorSmilgies, Detlef Matthiasen
dc.contributor.authorShkunov, Maxim N.en
dc.contributor.authorGenevičius, Kristijonasen
dc.contributor.authorWhitehead, Katherine S.en
dc.contributor.authorAmassian, Aramen
dc.contributor.authorMalliaras, George G.en
dc.contributor.authorBradley, Donal D Cen
dc.contributor.authorHeeney, Martin J.en
dc.contributor.authorCampbell, Alasdair J.en
dc.date.accessioned2015-08-04T07:04:47Zen
dc.date.available2015-08-04T07:04:47Zen
dc.date.issued2012-09en
dc.identifier.issn15671739en
dc.identifier.doi10.1016/j.cap.2011.07.042en
dc.identifier.urihttp://hdl.handle.net/10754/564596en
dc.description.abstract3′-methyl-(5,5′′-bis[3-ethyl-3-(6-phenyl-hexyloxymethyl) -oxetane])-2,2′:5′,2′′-terthiophene (5T(Me)Ox) is a solution processable small molecule semiconductor displaying smectic-C and nematic liquid crystal phases. The pendant oxetane group can be polymerized in situ in the presence of a suitable photoacid at concentrations ≥1% by weight. Spin-coated films of pure 5T(Me)Ox and 5T(Me)Ox doped with the soluble photoacid were characterized by absorption and photoluminescent spectroscopy. Thick pristine films showed absorption and emission from a crystalline phase. Thin monolayer (<5 nm) films, as well as thicker photoacid doped films, instead showed absorption from an H-aggregate phase and emission from an excimer. Optical microscopy showed a significant change in film structure upon addition of the photoacid; large and well-orientated crystals being replaced by much smaller domains which appear to vary in thickness. Grazing Incidence Wide Angle X-Ray Scattering (GIWAXS) was used to characterize the packing and orientation of molecules in the crystalline and doped samples. The results are consistent with the photoacid doped samples forming layers of H-aggregate phase monolayer sheets parallel to the substrate where the photoacid inhibits the transition into the three-dimensionally ordered crystalline phase. Field-effect transistors and light emitting diodes were constructed incorporating 5T(Me)Ox as the active layer. Pure 5T(Me)Ox field-effect transistors showed good, p-type device characteristics, but the morphological changes upon doping result in a loss of transistor action. In the diodes, curing through melting and exposure to UV light followed by photoacid removal resulted in an increase in current density but a decrease in light emission. These results indicate that the presence of the photoacid (≥1% by weight) can have a dramatic effect on the structure, morphology and device performance of ordered, photopatternable materials for organic electronics. © 2012 Elsevier Inc. All rights reserved.en
dc.publisherElsevier BVen
dc.subjectLiquid crystalen
dc.subjectOrganic electronicsen
dc.subjectOrganic field effect transistoren
dc.titleSpectroscopic and morphological investigation of conjugated photopolymerisable quinquethiophene liquid crystalsen
dc.typeConference Paperen
dc.contributor.departmentMaterials Science and Engineering Programen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.contributor.departmentSolar and Photovoltaic Engineering Research Center (SPERC)en
dc.contributor.departmentOrganic Electronics and Photovoltaics Groupen
dc.identifier.journalCurrent Applied Physicsen
dc.conference.nameInternational Workshop on Flexible & Printable Electronicsen
dc.contributor.institutionDepartment of Physics, Imperial College London, London SW7 2AZ, United Kingdomen
dc.contributor.institutionDepartment of Chemistry, Imperial College London, London SW7 2AZ, United Kingdomen
dc.contributor.institutionCornell High Energy Synchrotron Source (CHESS), Wilson Laboratory, Cornell University, Ithaca, NY 14853, United Statesen
dc.contributor.institutionMerck Chemicals Ltd, Southampton SO16 7QD, United Kingdomen
dc.contributor.institutionDepartment of Materials Science and Engineering, 327 Bard Hall, Cornell University, Ithaca, NY 14853, United Statesen
kaust.authorAmassian, Aramen
All Items in KAUST are protected by copyright, with all rights reserved, unless otherwise indicated.