Kazuo Takimiya

Thienoacenes consist of fused thiophene rings in a ladder-type molecular structure and have been intensively studied as potential organic semiconductors for organic field-effect transistors (OFETs) in the last decade. They are reviewed here. Despite their simple and similar molecular structures, the hitherto reported properties of thienoacene-based OFETs are rather diverse. This Review focuses on four classes of thienoacenes, which are classified in terms of their chemical structures, and elucid

The design, synthesis, and characterization of organic semiconductors applicable to organic electronic devices, such as organic field-effect transistors (OFETs) and organic photovoltaics (OPVs), had been one of the most important topics in materials chemistry in the past decade. Among the vast number of materials developed, much expectation had been placed on thienoacenes, which are rigid and planar structures formed by fusing thiophenes and other aromatic rings, as a promising candidate for org

Intermolecular hydrophobic interactions between long alkyl chains (fastener effect) can enhance the intermolecular overlap of the semiconducting layer of 2,7-dialkyl[1]benzothieno[3,2-b][1]benzothiophenes (Cn-BTBTs; n = 8, 10, 12), which contributes to improvements of the electric characteristics of their organic field-effect transistors. The molecular ordering of Cn-BTBTs in the thin-film state is elucidated by means of in-plane and out-of-plane X-ray diffraction of spin-coated thin films, and

Vapor-deposited thin films of a newly developed sulfur-containing heteroarene, 2,7-diphenyl[1]benzothieno[3,2-b][1]benzothiophene (DPh-BTBT), were used as an active layer of OFETs, which showed excellent FET characteristics in ambient conditions with mobilities of approximately 2.0 cm2 V-1 s-1 and Ion/Ioff of 107.

Patternable solution-crystallized organic transistors are developed with very high carrier mobility that exceeds 10 cm2 V−1 s−1. The devices feature a newly synthesized air-stable compound 2,9-didecyldi-naphtho[2,3-b:2’,3’-f]thieno[3,2-b]thiophene (C10-DNTT) and are formed from hot solution. A method of oriented growth is introduced to obtain the single-crystalline films of C10-DNTT, regulating the crystallizing direction and the positions in a single process. Detailed facts of importance to spe

A series of alkylated dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophenes (Cn-DNTTs) were developed as vapor-processable organic semiconductors for organic thin-film transistors (OTFTs). All the Cn-DNTT-based OTFTs showed typical p-channel FET characteristics and among them, C10-DNTT possessing two n-decyl groups gave excellent FET characteristics under the ambient conditions with mobility close to 8.0 cm2 V−1 s−1 and Ion/Ioff > 108. Detailed facts of importance to specialist readers are published a

Organic electronics has rapidly advanced in the last two decades, owing to the development of semiconducting materials and the innovation of device technologies. One of the critical issues in the materials development, for achieving high performances in the organic devices, is to precisely control their frontier orbitals, i.e., the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels. These energy levels are largely dependent on the chemical

2,6-Diphenylbenzo[1,2-b:4,5-b']dichalcogenophenes including thiophene, selenophene, and tellurophene analogues as organic semiconductors for field-effect transistors were effectively synthesized in three steps from commercially available 1,4-dibromobenzene. All three benzodichalcogenophenes acted as good p-type semiconductors, and particularly the selenophene analogue, 2,6-diphenylbenzo[1,2-b:4,5-b']diselenophene, showed high FET mobility of 0.17 cm2 V-1 s-1.

[1]Benzoselenopheno[3,2-b][1]benzoselenophene (BSBS) and its 2,7-diphenyl derivative (DPh-BSBS) were readily synthesized from diphenylacetylene and bis(biphenyl-4-yl)acetylene, respectively, with a newly developed straightforward selenocyclization protocol. In contrast to the parent BSBS that has poor film-forming properties, the diphenyl derivative DPh-BSBS formed a good thin film on the Si/SiO(2) substrate by vapor deposition. X-ray diffraction examination revealed that this film consists of h

Extended π system: A nickel(0)-mediated reaction afforded dinaphthopentalene derivatives, whose electronic and electrochemical properties depend on the fusion patterns. Very high hole mobility was observed for an amorphous material, and the compounds are applicable to organic heterojunction photovoltaic cells (see picture).

A thiazolothiazole-thiophene copolymer is examined as the active material in bulk heterojunction (BHJ) solar cells. By optimizing the molecular weight, the polymer-based cells exhibit power conversion efficiencies as high as 5.7%. The increase in molecular weight improves the orientational order, and blending with phenyl-C61-butyric acid methyl ester (PC61BM) changes the orientational motif from edge-on to face-on, which accounts for the trend in photovoltaic performances. These results might gi

The development of n-type conjugated polymers with high electrical conductivity (σ) has continued to pose a massive challenge in organic thermoelectrics (OTEs). New structural insights into the charge-carrier transport are necessitated for the realization of high-performance OTEs. In this study, three new n-type copolymers, named pNB, pNB-Tz, and pNB-TzDP, consisting of naphthodithiophenediimide (NDTI) and bithiopheneimide (BTI) units, are synthesized by direct arylation polymerization. The back

[reaction, structures: see text] A general and convenient synthesis of benzo[1,2-b:4,5-b']dichalcogenophenes including the thiophene (BDT, 1), selenophene (BDS, 2), and tellurophene (BDTe, 3) homologues is developed. Thus synthesized heterocycles are structurally characterized by single-crystal X-ray analysis, and all three homologues are isostructural with one another. They all have completely planar molecular structures packed in a herringbone arrangement. Their physicochemical properties were