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12 results on '"Gwinner, Michael C."'

11. Enhanced Ambipolar Charge Injection with Semiconducting Polymer/Carbon Nanotube Thin Films for Light-Emitting Transistors

Author

Gwinner, Michael C., Jakubka, Florian, Gannott, Florentina, Sirringhaus, Henning, and Zaumseil, Jana

Abstract

We investigate the influence of small amounts of semiconducting single-walled carbon nanotubes (SWNTs) dispersed in polyfluorenes such as poly(9,9-di-n-octylfluorene-alt-benzothiadiazole (F8BT) and poly(9,9-dioctylfluorene) (F8) on device characteristics of bottom contact/top gate ambipolar light-emitting field-effect transistors (LEFETs) based on these conjugated polymers. We find that the presence of SWNTs within the semiconducting layer at concentrations below the percolation limit significantly increases both hole and electron injection, even for a large band gap semiconductor like F8, without leading to significant luminescence quenching of the conjugated polymer. As a result of the reduced contact resistance and lower threshold voltages, larger ambipolar currents and thus brighter light emission are observed. We examine possible mechanisms of this effect such as energy level alignment, reduced bulk resistance above the contacts, and field-enhanced injection at the nanotube tips. The observed ambipolar injection improvement is applicable to most conjugated polymers in staggered transistor configurations or similar organic electronic devices where injection barriers are an issue.

Published
2012
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12. High-Performance Electron-Transporting Polymers Derived from a Heteroaryl Bis(trifluoroborate).

Author

Jin-Kyun Lee, Gwinner, Michael C., Berger, Reinhard, Newby, Carol, Zentel, Rudolf, Friend, Richard H., Sirringhaus, Henning, and Ober, Christopher K.

Subjects
*POLYMERS, *ELECTRON transport, *TRANSPORT theory, *MACROMOLECULES, *POLYCONDENSATION
Abstract

In this communication, we report that dipotassium aryl bis(trifluoroborate)s make stable and easy-to-purify yet reactive monomers under Suzuki polycondensation reactions. A bis(trifluoroborate) of 2-alkylbenzotriazole was prepared successfully and copolymerized with dibromobenzothiadiazole in the presence of a Pd catalyst and LiOH, yielding high molecular weight conjugated polymers. This polymer (P1) composed of all electron-accepting units shows excellent electron-transport properties (μe = 0.02 cm2 V-1 s-1), which proves the value of the aryl bis(trifluoroborate) monomers and suggests that many other types of semiconducting polymers that could not be accessed previously can be synthesized using this approach. [ABSTRACT FROM AUTHOR]

Published
2011
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