The effect of thiophene sequence separation on air-stable organic thin-film transistor materials

Abstract

The relationship between thiophene sequences and organic thin-film transistor (OTFT) characteristics was studied to determine their effect on ionization potential, molecular orientation, and air stability. Two types of molecular structures were used: continuous sequence and divided sequence thiophenes. The length of thiophene sequence did not affect FET characteristics but did affect ionic potential and air stability.Furthermore, materials with divided thiophene sequences showed no change in OTFT characteristics when exposed to air. These results suggest that separation of thiophene sequences can improve air stability, which is a problem of thiophene-based materials.

Influence of an Applied Electric Field on the Conduction Characteristics of a Bithienyl-Capped Biphenylene and Biphenyl-Capped Oligothiophenes in Organic Field-Effect Transistor Structures

“…In our experiments in this direct comparison, however, films of PPTTPP consistently showed a higher charge carrier mobility than films of TTPPTT in a sequence PPTPP << TTPPTT < PPTTPP in subtle correction of the results obtained earlier from the electrical characterization under differing conditions [6,7]. This sequence, however, finds itself in very good agreement with the optical fluorescence data which showed an enhanced π-overlap for PPTTPP relative to TTPPTT [2][3][4][5].…”

“…The electrical properties of thin evaporated films of PPTPP, PPTTPP, and TTPPTT ( Figure 1) have been studied before in separate sets of experiments in which the molecular thin films were prepared on different substrates and measured under different conditions [6,7]. By the field effect characteristics they were all characterized as p-type semiconductors under vacuum and also under air (probed for TTPPTT [7]).…”

“…By the field effect characteristics they were all characterized as p-type semiconductors under vacuum and also under air (probed for TTPPTT [7]). Comparing the results of these different reports the charge carrier mobility calculated from field-effect transistor characteristics increased in a sequence PPTPP << PPTTPP < TTPPTT.…”

“…This sequence does not reflect the higher π-electron interaction seen in the optical properties of PPTTPP relative to TTPPTT. Since, however, the values of mobility can depend on the experimental conditions, a comparison of the materials grown on identical substrates and measured under identical experimental conditions seems appropriate to provide a reliable ranking of the materials and to correlate these findings with the detailed optical and structural analysis discussed already in earlier reports [2,3,6,7]. …”

Synthesis of functionalized thiophene/phenyl co-oligomers by direct arylation of thiophenes

“…[2][3][4][5][6][7][8][9][10][11][12] In this respect, the combination of phenylenes and thiophenes has proven to be very successful in order to access optoelectronic devices with improved properties. [17][18][19][20][21][22][23][24][25][26][27][28] Compounds that are exclusively functionalized in position 4 of a terminal phenyl group and/or in position 2 of a terminal thiophene unit, however, are fairly rare, although they are also very promising candidates for the formation of nanoaggregates. Therefore, we started to develop a general approach for the synthesis of thiophenyl-phenylenes hybrid oligomers containing a total of three aromatic units and (at least) one biphenyl group as a reasonable compromise between interesting optical and optoelectronical properties on the one hand and solubility on the other hand.…”