Universally Exhaustive Generation of Molecular Structures and Prediction of Their Electronic States Using Machine Learning for N-type Organic Transistor Materials.

We have proposed a new method for the exploration of organic functional molecules, using an exhaustive molecular generator combined without combinatorial explosion and electronic state predicted by machine learning and adapted for developing n-type organic semiconductor molecules for field-effect transistors. Our method first enumerates skeletal structures as much as possible and next generates fused ring structures using substitution operations for atomic nodes and bond edges. We have succeeded in generating more than 4.

Liquid crystalline self-assembly of azulene-thiophene hybrids and their applications as OFET materials.

Orientational control within thin films is crucial for the preparation of organic field effect transistors (OFETs). The highly ordered liquid crystalline smectic E phase (SmE) is known as a powerful template for solution processed thin films. Here, we describe the synthesis and characterization of three novel azulene-thiophene hybrid materials.

Scalable Ultrahigh-Speed Fabrication of Uniform Polycrystalline Thin Films for Organic Transistors.

The fabrication of organic semiconductor thin films by printing technologies is expected to enable the low-cost production of devices such as flexible display drivers, RF-ID tags, and various chemical/biological sensors. However, large-scale high-speed fabrication of uniform semiconductor thin films with adequate electrical properties for these devices remains a big challenge. Herein, we demonstrate an ultrafast and scalable fabrication of uniform polycrystalline thin films with 100% surface coverage using liquid crystalline semiconductors such as 2-phenyl-7-decyl[1]benzothieno[3,2-][1]benzothiophene (Ph-BTBT-10) and 2.

Fabrication of planarly-oriented polycrystalline thin films of smectic liquid crystalline organic semiconductors.

Fabrication of planarly-oriented polycrystalline thin films of organic semiconductors was investigated, in which molecules sit parallel, i.e., "face-on" on the substrate so as to allow vertical charge transport favorably through a thin film.

Liquid crystals for organic thin-film transistors.

Crystalline thin films of organic semiconductors are a good candidate for field effect transistor (FET) materials in printed electronics. However, there are currently two main problems, which are associated with inhomogeneity and poor thermal durability of these films. Here we report that liquid crystalline materials exhibiting a highly ordered liquid crystal phase of smectic E (SmE) can solve both these problems.

Ambipolar transport in the smectic E phase of 2-propyl-5''-hexynylterthiophene derivative over a wide temperature range.

5-Hexyl-5''-hexynyl-2,2':5',2''-terthiophene exhibits the smectic E phase below 200 degrees C and does not crystallize when it is cooled to -100 degrees C. Between 200 and -100 degrees C, non-dispersive transport is observed for holes and electrons with time-of-flight spectroscopy. Over the entire temperature range, the electron mobility is approximately twice as high as that of the hole.

Reinvestigation of carrier transport properties in liquid crystalline 2-phenylbenzothiazole derivatives.

We have reinvestigated the charge carrier transport properties in a liquid crystal of 2-(4'-heptyloxyphenyl)-6-dodecylthiobenzothiazole (7O-PBT-S12), for which the electronic conduction was first established in rodlike liquid crystals and for which the highest hole mobility in the smectic A (SmA) phase ever achieved was reported. We found that 7O-PBT-S12 exhibited three crystal phases, one of which appeared in a limited temperature range of 10 degrees just below the phase transition temperature from the SmA phase. In this crystal phase, nondispersive transient photohole currents were observed in time-of-flight experiments, and its hole mobility was determined to be 8 x 10(-3) cm(2)/Vs, slightly higher than that reported previously in the SmA phase.

Electronic and ionic transports for negative charge carriers in smectic liquid crystalline photoconductor.

We have investigated negative charge carrier transport in the smectic mesophases of the 2-phenylnaphthalene derivative, 6-(4'-octylphenyl)-2-dodecyloxynaphthalene (8-PNP-O12), using the time-of-flight (TOF) method. We revealed that the negative charge carrier transport in its smectic mesophases had two different mechanisms, i.e.

Charge carrier transport properties in polymer liquid crystals containing oxadiazole and amine moieties in the same side chain.

Steady-state and transient photocurrent measurements were carried out to study the charge carrier transport properties of polymer liquid crystal (LC) containing oxadiazole (OXD) and amine moieties in the same side chain. The steady-state photocurrent measurement with asymmetric electrodes of ITO and Al and a short penetration depth of the illumination light indicated that both electrons and holes can be transported in this film. The transient hole photocurrent observed by time-of-flight (TOF) experiments was dispersive at room temperature.