Vertical phase separation of organic semiconductor/dielectric polymer blends has been used in field-effect transistors (FETs) to fabricate low-voltage devices, improve environmental stability, and reduce semiconductor cost. However, all structures reported in previous studies are dielectric-up and semiconductor-bottom structures, and it is difficult to combine multi-advantages in one system because special materials and methods are used in each case. Here, we first
fabricated a semiconductor-top and dielectric-bottom bilayer structure by surface-induced vertical phase separation of
conjugated molecules and insulating polymer blends. The use of these bilayered blends as active layer in FETs leads to an improvement of the device performance with a drastic reduction of semiconductor content because insulating polymer layer can act as modifier at the semiconductor/dielectric interface. Moreover, because the insulting polymer layer can be used as dielectric layer without any other dielectrics, the blended films can be used to fabricate high-performance, lowsemiconductor-content, and low-voltage FETs in a one-step process.
We have reported the fabrication of the self-organized 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS_PEN)
crystals with highly ordered molecular structures by using evaporation-induced flows in a solution process. The one-dimensional
microcrystal arrays of TIPS_PEN were fabricated by simple solution casting on a tilted substrate. By
pinning a solution droplet on the tilted substrate, an array of ribbon-shaped crystals aligned in the tilted direction was
formed on the substrate. In particular, self-aligned TIPS_PEN crystals with highly ordered crystalline structures via
inkjet printing were successfully produced by controlling the evaporation-induced flow using solvent mixture, and arise
when there is a recirculation flow in a inkjet printed droplet that is induced by a Marangoni flow (surface-tension-driven
flow) in the direction opposite to the outward convective flow. The field-effect transistors fabricated with these self-aligned
TIPS_PEN crystals via drop casting and inkjet printing exhibit significantly improved electrical performance.
These results demonstrate that control of evaporation-induced flow in a solution process of organic semiconductor can
be an excellent method for the production of organic semiconductor films with uniform morphology and desired
molecular orientation for the direct-write fabrication of high-performance OFETs.
Control over supramolecular organization of electronically active π-conjugated organic molecules provides great opportunities to fine-tune and optimize their electrical properties for applications in organic field-effect transistors and sensors. Here we report high-quality single-crystal organic semiconductors with conjugated organic molecules via facile solution processing. We show a well-faceted, high-quality 1D single-crystal microwire using self-organized poly (3-hexylthiophene), P3HT with unprecedented electrical characteristics such as a low resistance (0.5 MΩ), a channel current as high as 25 μA, and a well-resolved gate modulation via solution growth. Furthermore, we report the fabrication of high-quality 1D triisopropylsilylethynyl pentacene (TIPS_PEN) microribbons via a simple solution process with well-defined facets and remarkable electrical characteristics, such as field-effect mobility as high as 1.4 cm2/V.s. We found that 1D single-crystal microwires and microribbons are formed spontaneously through facile self-assembly of individual conjugated molecules. Our findings indicate that π-conjugated organic single-crystals are capable of very efficient charge transport.
Conference Committee Involvement (1)
Organic Field-Effect Transistors VI
26 August 2007 | San Diego, California, United States
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