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The crystallization and microstructure change of self-organization and the related conduction mechanisms of polymer semiconductor active thin layer in polymer organic field-effect transistors (OFET) are investigated by synchrotron radiation grazing incident X-ray diffraction (GIXRD) for understanding the relationships between polymer self-organization and charge carry. The change of the crystalline microstructure of RR-P3HT clarifies the effect of SAMs for improving the interface between the insulator layer and the organic semiconductor layer. The self-organiztion of RR-P3HT modified by SAMs improves the crystalliztion to pack form the thiophene rings along the perpendicular direction of substrate and results in that the π-π interchains are stacked to parallel the substrate. The two-dimensional charge transport is improved. Furthermore, we find that two-dimensional, conjugated, and self-organized crystalline lamellae are easier to gain with slow grown film than with fast grown film.

The contact effect on the performances of organic thin film transistors (OTFTs) is studied here. We fabricate Bottom-gated top-contact Pentacene-OTFTs on heavily doped n type Silicon wafers with using Al modified by MoO3 as source and drain electrodes. Field effect mobility μef of the OTFT reaches 0.42cm2/V ·s,the threshold voltage and the on/off current ratio arrive at -5.0 V and 4.7×103 respectively. The electric potential distribution in the channel is qualitively investigated by means of middle probe method (MPM) and the output curve is simulated by the charge drift method. Considering the contact effect,the μef is greatly improved to 1.1 cm2/V ·s,which indicates the importance of the contact engineering in OTFTs.