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

Abstract

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.

Comparative study of soluble naphthalene diimide derivatives bearing long alkyl chains as n-type organic thin-film transistor materials

“…In accordance with our former report, the higher molecular mobility due to the shorter alkyl chains leads to excessive thin-film reconstructions, which results in defective thin films having deficient parts because molecules have migrated to other parts. [18] From this perspective, NTCDI-C13 must be the optimal n-type material, with its relatively high electron  FE and wet-process capability.…”

“…annealing above the transition temperature to their LC phase, because of dramatic changes in film morphology. [18,35] We believe that the  FE enhancements and morphological changes after annealing partly result from high molecular mobility in the LC phase, although another factor might also be responsible because the enhancement and morphological changes were observed even at a T A of 100 C. The small molecular size of the NTCDI core, whose molecular weight is 266 g/mol, compared with that of PTCDI might influence the high molecular mobility, which is crucial for dramatic morphological changes.…”

“…[12] Perylene tetracarboxylic acid diimides (PTCDIs) are among the most promising n-channel candidates for organic TFTs because of their high electron affinity and large π-orbital overlap in the solid state. [9,10,[13][14][15][16][17][18][19] Many substituents have been introduced in PTCDIs to, for example, improve electron mobility, enlarge electron affinity for operation stability in air, and improve solubility in common solvents.…”

N,N′-diphenylperylene diimide functioning as a sensitizing light absorber based on excitation transfer for organic thin-film solar cells

“…This makes sense from the standpoint of the n-type organic transistor behavior of PTCDI-Ph [19] and other PTCDI derivatives. [20][21][22][23][24] However, J SC was lower for the 40-nm thick layer than for the 30-nm thick layer. Note that the non-BP3T cell exhibited much worse performance than the others with the PTCDI-Ph layers, which indicates that the BP3T/C 60 junction mainly causes charge separation in the cells comprising BP3T, C 60 , and PTCDI-Ph.…”

Wet-processed n-type OTFTs utilizing highly-stable colloids of a perylene diimide derivative

“…It, especially, has several phase transitions at relatively low temperature due to the long side alkyl chains, and the morphology of vacuum deposited films is largely changed by post-annealing treatment which also leads to the large change in the mobility of its devices [32,36,37]. It is, however, not soluble in common solvents and cannot be handled by wet-processes.…”