Thermal treatment effects on N-alkyl perylene diimide thin-film transistors with different alkyl chain

摘要

The authors report that thermal treatment effect on various N,N'-dialkyl-3,4,9,10-perylene tetracarbxylic diimides [PTCDI-Cn, alkyl-dodecyl (n=12), butadecyl (n=14), octadecyl (n=18)] thin-film transistors (TFTs) 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 ℃.