Pentacene OTFT Properties

The reason for pentacene being superior for the production of TFT devices [7, 8] when compared with other molecules [9] is still not obvious. In this chapter, we will discuss to what extent the peculiar growth properties [10] of pentacene on metallic contacts and gate dielectrics contribute to the device performance. For this purpose, first the early growth state of pentacene films and the molecular structure of the so called thin film phase is reviewed. Then, major sources of crystal defects in thin films as determined by advanced synchrotron diffiaction techniques are discussed. The relation of these defects to the frequently discussed electronic traps that strongly influence transport properties of TFTs [6, 11, 12] is indicated. Finally, the spatially resolved photo response of pentacene OTFTs will be discussed in the context of injection barriers and contact homogeneity. 

A -sulfinylacetamide 297 in greater than 90% yield when a catalytic amount of methyltrioxorhenium is employed. Futhermore, the hetero-Diels-Alder adduct is highly soluble in both chlorinated and ethereal solvents. A detailed investigation of the retro-Diels-Alder reaction of 298 by thermogravimetric analysis revealed an onset temperature of 120 °C and complete conversion of bicycle 298 to pentacene 296 at 160 °C, which are temperatures compatible with the polymer supports typically used in electronics applications. The electronic properties of these newly prepared OTFTs are similar to those prepared by traditional methods. Later improvements to this chemistry included the use of A -sulfinyl-/< r/-butylcarbamate 299 as the dienophile <2004JA12740>. The retro-Diels-Alder reaction of substrate 300 proceeds at much lower temperatures (130 °C, 5 min with FlTcatalyst 150 °C, Ih with no catalyst). 

We observe a strong photo response localised at the anode [52]. The response is inhomogenous along the contact indicating variations in the transport or injection properties of the device. These variations may be due to local variations of the contact work function, or due to bad physical contact of the pentacene grains adjacent to the electrode, or due to a local enhancement of defect densities in the pentacene film. Thus, a systematic study of the photo response in combination with the respective characteristic transistor curves allows visualising problematic regions of an OTFT, which is a key prerequisite for device optimisation. 

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