No abstract

We study the stability in time of the current–voltage characteristics of organic thin-film devices on glass substrates. We find for poly(3-hexylthiophene) and for pentacene that the resistance of the devices gradually changes under the application of an electrical bias depending on the sodium content of the glass substrates used in the experiment. For devices on a very common type of glass (with a Na2O content of about 6%) and on sodalime glass (14% Na2O) substrates, the prolonged application of a voltage bias results in a substantial decrease (up to two orders of magnitude) of the bulk and contact resistances, whereas for sodium-free glass substrates the gradual changes in current–voltage characteristics are much smaller. A systematic study of the electrical behavior complemented by chemical analysis shows that the instabilities observed are due to Na+ ions diffusing from the substrate into the organic film, and moving inside the organic material as a result of the applied electric field. Our results show in detail how ion motion in organic materials results in substantial hysteresis and device instabilities.

No abstract

Hydrogen bonds between urea units allow self-organization of π systems in mono- and bithiophenes into fibers as shown schematically. In these fibers there is a surprisingly high mobility of charge carriers as determined by pulse-radiolysis time-resolved microwave conductivity measurements.

CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Lower limits of the intrinsic charge carrier mobility in the solid phase of a series of oligothiophene compounds were determined with the pulse-radiolysis time-resolved microwave conductivity technique, PR-TRMC. The mobility values fall roughly into two regimes and show no correlation with the number of conjugated thiophene units. Relatively low mobilities (in the range of 3-6 10" cm?Vs) were found for a series of cyclohexyl-endcapped thiophenes, while significantly higher values of 0.01-0.02 cm'/Vs were obtained for several n-hexyl and n-dodecyl substituted compounds and for sexithiophene. Interestingly, these latter values are similar to those of n-alkyl substituted polythiophenes measured earlier.