Naoyuki Yamasaki

Solution Processable Organic Solar Cell Based on Bulk Heterojunction Utilizing Phthalocyanine Derivative

Organic thin-film solar cells based on a bulk heterojunction utilizing the phthalocyanine derivative 1,4,8,11,15,18,22,25-octahexylphthalocyanine (C6PcH2) have been studied. C6PcH2 is soluble in common organic solvents such as chloroform, and the blend uniform thin film with the fullerene derivative 1-(3-methoxy-carbonyl)-propyl-1-1-phenyl-(6,6)C61 (PCBM) could be fabricated by a spin-coating method. Solar cells with an indium–tin-oxide/polymer hole transport layer/C6PcH2:PCBM/Al structure, the active layer of which was prepared by a wet process using a low-weighted molecular system, have demonstrated a high external quantum efficiency of more than 70% in the Q-band absorption region of C6PcH2 and a high energy conversion efficiency of 3.1%.

High Carrier Mobility up to 1.4 cm2·V-1·s-1in Non-Peripheral Octahexyl Phthalocyanine

Carrier transport properties of a non-peripherally alkyl-substituted phthalocyanine, 1,4,8,11,15,18,22,25-octahexylphthalocyanine (C6PcH2) have been investigated. The material is a low-molecular-weight organic semiconductor with high solubility for typical organic solvents and liquid crystallinity. The carrier mobility was measured in the crystal phase and the hexagonal disordered columnar (Colhd) mesophase by the time-of-flight technique. A strong negative temperature dependence was observed for the hole mobility in the crystal phase, and a maximum drift mobility of 1.4 cm2·V-1·s-1 was achieved at -15 °C. A maximum mobility of 0.5 cm2·V-1·s-1 was obtained for the electrons that had a smaller dependence.

Anisotropic Properties of Aligned

Uniaxially aligned films of thiophene-based polymers were successfully fabricated by a novel film-forming method using the capillary action of polymer solutions without applying any mechanical or thermal stress to the polymers. Unique optical and electrical anisotropies were studied in the poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene) (pBTTT) and poly(2,5-bis(3-alkylthiophene-2-yl)thieno[2,3-b]thiophene) (pBTCT) films fabricated by the method. Moreover, the improvements of the optical and electrical properties of the aligned polymer films by thermal annealing were also demonstrated.

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The effect of column disorder on carrier drift mobility in columnar discotic liquid crystals has been investigated by applying a precisely controlled oscillating shear stress. Drift mobilities on the order of 10-1 cm2?V-1?s-1 were confirmed for positive and negative carriers in the columnar phase of 1,4,8,11,15,18,22,25-octahexylphthalocyanine in a well-aligned homeotropic geometry, in which the columnar axis was perfectly perpendicular to substrates with an electrode. A slight tilt of the columnar axis upon applying shear stress led to a marked decrease in electronic carrier mobility from 10-1 to less than 10-6 cm2?V-1?s-1, and transport was only confirmed for positive ion carriers. This result indicates that a uniform shear stress blocks the carrier transport path in the entire area of the electrode, and one-dimensional carrier transport path along the columns is easily hindered in columnar discotic liquid crystals.

-Conjugated Polymer Films Fabricated by Capillary Action and Their Post-Annealing Effects

The fabrication of oriented π-conjugated polymer films by a novel film-forming method has been studied. We succeeded in fabricating uniaxially oriented π-conjugated polymer films utilizing substrates with a geometrically-asymmetric sandwich structure, which could produce a unidirectional solution flow by capillary action. The optical and electrical anisotropies have been investigated in π-conjugated polymer films fabricated by the method, and discussed by taking the polymer orientation into consideration.

Effect of Column Disorder on Carrier Transport in Columnar Discotic Liquid Crystal Evaluated by Applying Precisely Controlled Shear Stress

High-quality planar alignment was achieved in the hexagonal columnar phase of 2,3,6,7,10,11-hexahexyloxytriphenylene by applying an oscillating shear using a piezoelectric actuator. Discotic liquid crystals with thicknesses up to 38 ?m could be aligned using this technique, with the molecular columns aligning parallel to the direction of the shear. The quality of the alignment was also found to be higher in this technique than in previously proposed alignment methods, since a higher retardation and a higher dichroic ratio were obtained.

Solution Flow Assisted Fabrication Method of Oriented π-Conjugated Polymer Films by Using Geometrically-Asymmetric Sandwich Structures

The goal of this study is to evaluate the structural stiffness of cornea, toward the accurate sensing of the internal eye pressure. For this purpose, we design and develop the eye dynamic sensing system composed of a high-speed camera, and a non-contact tonometer for imparting an air puff to eye. Through experiments, we found an interesting tendency where deformation of central cornea in aged people is more than that in younger people.

High-Quality Planar Alignment of Discotic Liquid Crystals Using Oscillating Shear

The emission properties of π-conjugated polymers based on 9,10-dihydrophenanthrene units, which are expected to form linear and planar π-conjugations and have rigid characteristics in the main chain, have been clarified in the films. The photoluminescence decay of the π-conjugated polymers with the 9,10-dihydrophenanthrene unit has been studied in detail, and low-threshold photopumped multimode blue laser emission has been demonstrated from cylindrical microcavities with the polymer thin film fabricated onto the inner surface of an optical capillary tube.

Is Cornea Compliant with respect to Age

Thermal annealing effects of the aligned thiophene-based polymer films were studied. Aligned poly2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene (pBTTT) and poly2,5-bis(3-alkylthiophene-2-yl)thieno[2,3-b]thiophene (pBTCT) films were fabricated by utilizing capillary actions of polymer solutions. The optical anisotropies of the aligned films were enhanced by thermal annealing at temperatures below the phase transition. The differences in the optical anisotropies between pBTTT and pBTCT were discussed by taking the lamellar stacking structures in the aligned films and phase transition into consideration.

Time-Resolved Photoluminescence Study and Microcapillary Laser of Blue-Emissive π-Conjugated Polymers Based on 9,10-Dihydrophenanthrene Unit

The optical and electrical properties of polymer composite films based on poly(2-methoxy-5-dodecyloxy-p-phenylenevinylene) (MDDOPPV) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) have been studied. We investigated the time-resolved photoluminescence of the composite films and clarified the rapid intermolecular energy transfer from F8BT to MDDOPPV. As a result of the utilization of the polymer composite thin film as the emission layer of a light-emitting diode, a 23-fold increase in luminance was observed in comparison to that with a non composite MDDOPPV emission layer.