The authors report that thermal treatment effect on various N , NЈ-dialkyl-3,4,9,10-perylene tetracarbxylic diimides ͓PTCDI-Cn, alkyl-dodecyl ͑n=12͒, butadecyl ͑n=14͒, octadecyl ͑n=18͔͒ thin-film transistors ͑TFTs͒ depends on the substituted alkyl chain length. It is clearly demonstrated that there are two kinds of molecular movements during the thermal treatment on PTCDI films; molecular rearrangement in the same layer and molecular migration from the lower layer to the upper layer. The former is directly related to the grain growth and can be controllable by applying an external electric field. The latter is also related not only to the grain growth but also to the formation of cracks between grains. These two movements show opposite dependence on the alkyl chain length during the thermal treatment; the former is more active in longer alkyl chain, but the latter in shorter one. However, they also have opposite effect to TFT performance, and PTCDI films with longer alkyl chains have great advantage on TFT performance for the thermal treatment. Consequently, PTCDI-C18 TFTs show the highest electron mobility as large as 1.2 cm 2 / V s after the thermal treatment at 140°C.

The authors report a novel perylene derivative [N,N '-bis(3-dodecyloxy-propyl)-perylene tetracarboxylic diimide, PTCDI-C3OC12] as a soluble high-performance n-type organic semiconductor. The solubility of the PTCDI derivative was increased sufficiently to be handled using wet processes by inserting ether groups in side alkyl chains of the PTCDI derivative. The highest electron mobility obtained for a spin-coated PTCDI-C3OC12 film was 0.52 cm2/(V·s) with a very low threshold voltage of ca. 2 V. This high performance of PTCDI-C3OC12 is explained by the large grain size with an appropriate molecular packing pattern and tight intergrain connections.

Fused thiophene-split oligothiophenes were synthesized by Suzuki coupling. The relationship between the structure of these fused thiophene-split oligothiophenes and DH-6T (α,ω-dihexylsexithiophene) and their performance in OTFTs was discussed. The realignment of HTTfTTTH (2,5-Bis-(5'-hexyl-[2,2']bithiophenyl-5-yl)-thieno[3,2-b] thiophene) molecule on the substrate after annealing was revealed by X-ray diffraction and atomic force microscopy. A similar but novel compound, TTfTTT (2,5-Bis-[2,2']bithiophenyl-5-yl-thieno[3,2-b]thiophene), was also prepared and evaluated as an organic transistor material. Air stabilities of these three compounds in OTFT devices were affected mainly by chemical properties, but also by the ionization potentials (I p ) of these materials. Among the three compounds, HTTfTTTH had a higher I p because the thiophene sequence was split by fused thiophene and the best air stability, due to the end-capping of its active α-positions by hexyl substitution.