The rapidly expanding field of organic semiconductors for display and low-cost electronic applications requires materials, which not only have high mobility but also benefit from solution processability and environmental stability. In this paper we present a new class of solution coatable organic materials with excellent stability to air and light. Spin-coated FET devices operate at ambient conditions without encapsulation and show p-type field-effect mobilities of 2 x 10-3 cm2V-1s-1 and on/off ratios greater than 104. Thin films can be deposited from common organic solvents onto a variety of substrates. These films are mechanically robust and can withstand temperatures in excess of 100 °C without significant changes in electrical performance. FET switching and transient characteristics at higher frequencies are also discussed. These types of materials should find applications in many areas of flexible electronics.

High mobility organic semiconductor formulations with excellent uniformity across large area substrates are prepared via the use of formulations containing small molecule and high permittivity semiconducting oligomers. The use of these high-k ( k > 3.3) oligomers allows control of the wetting via the manipulation of the surface energy of the substrate being coated. Organic thin fi lm transistors results with mobilities of up to 5 cm 2 V −1 s −1 , standard deviation <10 %, on/off ratios of 10 9 are presented.

the manufacturing processes divide naturally into two general approaches i.e., solution-processing and vacuum processing. In the former approach some or all transistor and circuit elements are deposited from solution and holds out the promise of low-cost, high-volume roll-to-roll (R2R) manufacture of circuits using, for example, inkjet [ 7 ] or gravure printing. [ 8 ] On the other hand, processes requiring vacuum evaporation of one or more component, or photolithography and dry-etching are more suited to batch-processing.Progress has been, and continues to be made, in applying mass-printing R2R processes [ 9 ] with a range of logic circuits being demonstrated [ 10 ] albeit based on singlewalled carbon nanotubes as the active material. High-speed metal patterning and barrier layer deposition are commercially used processes. R2R circuit fabrication based entirely on vacuum evaporation is, therefore, feasible. [ 11 ] For example, saturated-load unipolar ring oscillators (ROs) were produced in a R2R-compatible environment. [ 12 ] Although a stage delay of 46 µs was achieved at a high supply voltage, circuit performance was compromised by a nonoptimal design purposely limited to the resolution and registration capability of a high-speed metal printing process. Nevertheless, the stage delay achieved was much shorter than previously reported for ROs produced using all-solution mass-printing processes ( Table 1 ) . [13][14][15] This refl ects the generally higher mobilities of vacuum-evaporated small-molecules [ 12 ] compared with solutionprocessed small-molecules. [ 16,17 ] Other performance-degrading features of solution R2R-processes include a relatively thick dielectric layer and relatively poor resolution. The former leads to high operating voltages. The latter reduces operating speed by restricting the source-drain gap, i.e., the channel length, L , of the OTFTs to a minimum of about 30-40 µm. Achieving a resolution below ≈10 µm to improve device speed poses a signifi cant near-term challenge for mass-printing processes. Relatively poor registration between different patterned layers is a further problem leading to undesirable parasitic effects. [ 12 ] It is not surprising, therefore, that the signifi cant improvements in organic circuit performances have been demonstrated using the higher resolution approaches derived from silicon technology. At the most basic level, this is confi ned to patterning source-drain electrodes by photolithography to achieve channel lengths of 5 µm High-frequency ring oscillators with sub-microsecond stage delay fabricated from spin-coated fi lms of a specially formulated small-molecule/host-polymer blend are reported. Contacts and interconnects are patterned by photolithography with plasma etching used for creating vias and removing excess material to reduce parasitic effects. The characteristics of transistors with 4.6 µm channel length scale linearly with channel width over the range 60-2160 µm. Model device parameters extracted using Silvaco's Universal Organic Thin Film Transistor...

The synthetic challenge and pronounced biological activity of the complex trichothecene mycotoxins have combined to generate intense interest in this family of compounds.' The employment of Diels-Alder cycloaddition between methyl coumalate (1) and various dienes as key steps in certain syntheses2 and synthetic approaches3 to these toxins prompts us to report some preliminary observations in this area.Cycloaddition of methyl coumalate with isoprene has been reported4 to produce the adduct (3) in modest yield. More recent studies,5 employing 13C n.m.r. spectroscopy, detected the additional presence of the regioisomer ( 5 ) , with a regioisomeric ratio of 10 : 1 in favour of (3). As partial proof of structure, the major isomer (3) was reported on iodolactonisation to produce the lactone (7), which surprisingly did not undergo base-induced elimination of HI.

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