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A Quantitative Correlation between the Mobility and Crystallinity of Photo-Cross-Linkable P3HT
journal contribution
posted on 2012-04-10, 00:00 authored by Claire
H. Woo, Claudia Piliego, Thomas W. Holcombe, Michael F. Toney, Jean M. J. FréchetThe performance of polymer field effect transistors (FETs)
can vary by orders of magnitude by applying different processing conditions.
Although it is generally believed that a higher degree of crystallinity
results in a higher mobility, the correlation is not straightforward.
In addition, the effect of cross-linking on polymer thin film microstructural
order is relatively unknown. This study investigates the effect of
thermal annealing and UV-initiated photo-cross-linking on the FET
performance and microstructural order of a photo-cross-linkable P3HT
derivative. Our results demonstrate that while cross-linking did not
disrupt the overall crystallinity of the polymer thin film, the photo-cross-linking
process likely induced doping in the semiconductor layer, leading
to the absence of saturation behavior in the FET. Annealing after
cross-linking slightly improved the FET performance but only minimally
affected the microstructural order of the polymer film since the 3D
morphology had been “locked in” during the first cross-linking
step. Importantly, annealing and cross-linking simultaneously was
a successful method to preserve polymer crystallinity while also achieving
effective cross-linking. Using newly developed quantitative X-ray
analysis techniques, our study established a quantitative correlation
between FET charge mobility and thin film crystallinity.