Field-effect transistors made of organic single crystals are ideal for studying the charge transport characteristics of organic semiconductor materials. Their outstanding device performance, relative to that of transistors made of organic thin films, makes them also attractive candidates for electronic applications such as active matrix displays and sensor arrays. These applications require minimal cross-talk between neighbouring devices. In the case of thin film systems, simple patterning of the active semiconductor layer minimizes cross-talk. But when using organic single crystals, the only approach currently available for creating arrays of separate devices is manual selection and placing of individual crystals-a process prohibitive for producing devices at high density and with reasonable throughput. In contrast, inorganic crystals have been grown in extended arrays, and efficient and large-area fabrication of silicon crystalline islands with high mobilities for electronic applications has been reported. Here we describe a method for effectively fabricating large arrays of single crystals of a wide range of organic semiconductor materials directly onto transistor source-drain electrodes. We find that film domains of octadecyltriethoxysilane microcontact-printed onto either clean Si/SiO(2) surfaces or flexible plastic provide control over the nucleation of vapour-grown organic single crystals. This allows us to fabricate large arrays of high-performance organic single-crystal field-effect transistors with mobilities as high as 2.4 cm(2) V(-1) s(-1) and on/off ratios greater than 10(7), and devices on flexible substrates that retain their performance after significant bending. These results suggest that our fabrication approach constitutes a promising step that might ultimately allow us to utilize high-performance organic single-crystal field-effect transistors for large-area electronics applications.

No abstract

Short conjugated phenylene (P)−thiophene (T) oligomers with varying α and ω alkyl and alkoxy substitutions were synthesized using Stille and Suzuki coupling reactions to investigate the correlation between end-group structure and electronic properties on P2TP and P3TP conjugated cores. Several soluble oligomers were synthesized with 5,5‘-bis(4-n-octylphenyl)-2,2‘-bithiophene (do-PTTP) showing the highest mobility (μ = 0.18 cm2 V-1 s-1) and on/off ratio of 107 at a substrate temperature of 50 °C. Thin film morphologies analyzed using atomic force microscopy revealed higher nucleation densities for branched alkoxy side-chain molecules compared to those of their straight alkyl side-chain counterparts. Field-effect mobility showed an inverse correlation to side-group bulkiness, indicating a strong morphological component to charge transport in the P2TP and P3TP series.

A series of phenylene–fluorene derivatives (see figure) are synthesized and evaluated for use in organic field‐effect transistors. Average field‐effect mobilities as high as 0.32 cm2 V–1 s–1 are achieved by vacuum deposition at low substrate temperatures. The high ionization potentials in the derivatives lead to improved chemical and photostability. Transistor devices show no loss in performance when tested over a period of three months.