Organic material combines ferroelectric switching with on-demand polymerization
Researchers created a hybrid organic material that switches electrical polarity while simultaneously building a semiconducting polymer layer at its electrodes. The dual-function capability could enable simpler, cheaper organic diodes and energy storage devices by eliminating the need for separate polymerization steps.
Originaltitel: Ferroelectric Switching and Electrochemistry of Pyrrole Substituted Trialkylbenzene-1,3,5-Tricarboxamides
Organiska ferroelektriska dioder baserade på bensentrikarboxamider öppnar vägen för flexibla elektronikkomponenter med låg tillverkningskostnad. Forskarna vid Eindhoven University of Technology och Linköpings universitet utvecklade en BTA-molekyl med pyrrolgrupper som under elektrokemisk cykling polymeriseras till ledande polypyrrol. Materialet uppvisar en hexagonal kolumnär flytande kristallin fas och kan växla sitt elektriskt tillstånd. Vid låga omkopplingsfrekvenser uppstår oxidativ polymerisation som genererar en laddningstäthet på cirka 1000 mC/m². Polymerisökningen begränsas till cirka 17 nanometer tjocka elektrodlager efter 21 timmars cykling. För leverantörer av organiska material och komponenttillverkare inom flexibel elektronik är resultatet relevant för utveckling av fuktkänsliga och miljövänliga diodsystem. Tidshorisont till industriell tillämpning är dock långsiktig.
<p>We explore a new approach to organic ferroelectric diodes using a benzene-tricarboxamide (BTA) core connected with C10 alkyl chains to pyrrole groups, which can be polymerized to provide a semiconducting ferroelectric material. The compound possesses a columnar hexagonal liquid crystalline (LC) phase and exhibits ferroelectric switching. At low switching frequencies, an additional process occurs, which leads to a high hysteretic charge density of up to similar to 1000 mC/m(2). Based on its slow rate, the formation of gas bubbles, and the emergence of characteristic polypyrrole absorption bands in the UV-Vis-NIR, the additional process is identified as the oxidative polymerization of pyrrole groups, enabled by the presence of amide groups. Polymerization of the pyrrole groups, which is essential to obtain semiconductivity, is limited to thin layers at the electrodes, amounting to similar to 17 nm after cycling for 21 h. (C) 2017 The Authors. Journal of Polymer Science Part B: Polymer Physics Published by Wiley Periodicals, Inc.</p>