Effect of molecular orientation on carrier transport in organic field‐effect transistors based on newly synthesized liquid crystalline compounds

Abstract

We fabricated organic field‐effect transistors (OFETs) based on the liquid crystalline compound which was newly synthesized to enhance carrier‐transport ability. Large conduction anisotropy depending on the carrier‐transport channels was observed in the OFETs fabricated using oblique evaporation, which was probably due to the anisotropic molecular alignment in the liquid crystalline films. The carrier‐transport properties of OFETs depended on the deposition rate of liquid crystalline materials. The mobilities increased up to 2.6×10–2 cm2/Vs as the deposition rates decreased. To estimate the degree of molecular orientation in liquid crystalline films with different deposition rates, polarization‐resolved photoluminescence was measured, and we found that the molecular orientation improved with decrease in the deposition rate. Atomic force microscopy was performed for liquid crystalline films with different deposition rates, and we did not observe large differences of surface features depending on the deposition rates, suggesting that the deposition rate influenced more significantly on the molecular orientation than the surface features in the liquid crystalline films. Therefore, it is assumed that the carrier‐transport properties of OFETs were enhanced by improving the molecular orientation in the liquid crystalline films. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

High Performance OTFTs Fabricated Using a Calamitic Liquid Crystalline Material of 2‐(4‐Dodecyl phenyl)[1]benzothieno[3,2‐b][1]benzothiophene

“…However, it remains challenging to control the thickness and the crystal orientaion of the single crystals. Recently, liquid‐crystalline materials have been considered as promising candidates for OTFTs because these materials can form well‐ordered polycrystalline thin films with large aligned domains as‐deposited or after thermal annealing to promote structuring in liquid‐crystalline phases . Self‐assembly with high degrees of intermolecular order facilitates charge transport in organic semiconductors.…”

Synthesis and properties of new liquid crystals derivatives of 2,7-diethynyl-9,9-dihexylfluorene

“…Luminescent materials based on polymers, oligomers and low molar weight molecules with liquid crystalline properties have been studied and used in the development of devices such as organic light-emitting diodes and organic field effect transistors [1][2][3][4][5].…”

Single crystalline growth of a soluble organic semiconductor in a parallel aligned liquid crystal solvent using rubbing-treated polyimide films

“…Generally, single crystals composed of organic molecules have anisotropic carrier transport characteristics because the π-π molecular interaction among molecules is different along each crystalline axis. [9][10][11] For this reason, a directional control technique for organic single crystals is required for optimizing carrier transport characteristics between source and drain electrodes. However, there has been little development in the area of solution-based single-crystal growth techniques.…”