Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

DOI： 10.1246/bcsj.20220093

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1038/s41428-021-00497-9

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Other Link： https://www.nature.com/articles/s41428-021-00497-9

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

Cis-to-transisomerization of poly (thienylenevinylene) is found to be a viable fabrication method for semiconducting trans-poly(thienylenevinylene) (trans-P1) thin films. Specifically, thin films of trans-P1, an alternating copolymer containing isoindigo and (E)-1,2-dithienylethene units, which are well known as an excellent p-type semiconductor, were prepared by thermally annealing thin films of the cis-poly(thienylenevinylene) (cis-P1) isomer (92% cis) at 240 degrees C for 30 min. The hole mobility of the isomerized films is comparable to that of films prepared from spin-coated solutions of the trans-isomer. Taking advantage of the greater solubility of the cis-isomer, it was possible to replace the toxic halogenated solvents normally needed for the dissolution of trans-P1 with the environmentally friendly 2-MeTHF. Solid-state cis-to-trans isomerization is therefore a potentially attractive fabrication option for the commercial development of sustainable, printable electronics.

DOI： 10.1021/acs.chemmater.1c01016

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

We report the design, synthesis, and physicochemical properties of an array of phenanthro[2,1-b:7,8-b’]dithiophene (PDT-2) derivatives by introducing five types of alkyl (CnH2n+1; n = 8, 10, 12, 13, and 14) or two types of decylthienyl groups at 2,7-positions of the PDT-2 core. Systematic investigation revealed that the alkyl length and the type of side chains have a great effect on the physicochemical properties. For alkylated PDT-2, the solubility was gradually decreased as the chain length was increased. For instance, C8-PDT-2 exhibited the highest solubility (5.0 g/L) in chloroform. Additionally, substitution with 5-decylthienyl groups showed poor solubility in both chloroform and toluene, whereas PDT-2 with 4-decylthienyl groups resulted in higher solubility. Furthermore, UV-vis absorption of PDT-2 derivatives substituted by decylthienyl groups showed a redshift, indicating the extension of their π-conjugation length. This work reveals that modification of the conjugated core by alkyl or decylthienyl side chains may be an efficient strategy by which to change the physicochemical properties, which might lead to the development of high-performance organic semiconductors.

DOI： 10.3390/molecules25173842

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Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

To investigate organic field-effect transistor (OFET) properties, a new thienoacene-type molecule, 4,14-dihexyldinaphtho[2,3-d:2’,3’-d’]anthra[1,2-b:5,6-b’]dithiophene (C6-DNADT), consisting of π-conjugated nine aromatic rings and two hexyl chains along the longitudinal molecular axis has been successfully synthesized by sequential reactions, including Negishi coupling, epoxidation, and cycloaromatization. The fabricated OFET using thin films of C6-DNADT exhibited p-channel FET properties with field-effect mobilities (µ) of up to 2.6 × 10−2 cm2 V−1 s−1, which is ca. three times lower than that of the parent DNADT molecule (8.5 × 10−2 cm2 V−1 s−1). Although this result implies that the installation of relatively short alkyl chains into the DNADT core is not suitable for transistor application, the origins for the FET performance obtained in this work is fully discussed, based on theoretical calculations and solid-state structure of C6-DNADT by grazing incidence wide-angle X-ray scattering (GIWAXS) and atomic force microscopy (AFM) analyses. The results obtained in this study disclose the effect of alkyl chains introduced onto the molecule on transistor characteristics.

DOI： 10.3390/ijms21072447

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Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

DOI： 10.1246/cl.190304

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>A new class of an acceptor unit, vinylene-bridged 5,6-difluorobenzothiadiazole <bold>FBTzE</bold>, and three <bold>FBTzE</bold>-containing copolymers has been synthesized and characterized.</p>

DOI： 10.1039/c8tc05764h

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.joc.8b02557

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Publishing type：Research paper (scientific journal)  

© 2019 The Chemical Society of Japan. Bis[1]benzothieno[5,4-d:5¤,4¤-d¤]benzo[1,2-b:4,5-b¤]dithiophene (BBTBDT-2) and its phenyl-substituted derivative were successfully synthesized and characterized. From DFT calculations, highest occupied molecular orbitals (HOMOs) of both compounds are well delocalized and large orbital coefficients exist on sulfur atoms. Single-crystal X-ray analysis revealed that BBTBDT-2 derivatives formed herringbone structures in the solid state. In particular, BBTBDT-2 formed a layer-by-layer structure with effective 2D charge-carrier transporting capability. The fabricated OFETs based on BBTBDT-2 gave mobility up to 0.49 cm2 V11 s11 in the vacuum-deposited thin films, which is the highest value among BBTBDT derivatives including our previously reported syn-counterparts. We have also clarified a detailed structureproperty relationship of sulfur positions and phenyl substituents as indicated by theoretical calculation, GIWAXS, and AFM analyses.

DOI： 10.1246/bcsj.20180358

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：John Wiley and Sons Inc.  

The synthesis, characterization, and solar cell application of newly developed two semiconducting polymers containing phenanthro[1,2-b:8,7-b′]dithiophene (PDT) and an isoindigo (IID) unit are described. In addition, a relationship between substitution position of side chains and molecular weights of the polymers and their solar cell performance are also discussed. Because of the installation of alkyl side chains onto sterically less hindered positions, PDT-IID copolymers 12OD-2 and 8OD-2 have stronger intermolecular interaction than that of the previously reported copolymer 12OD. In low-Mn polymers 12OD-2 and 8OD-2 formed high-crystalline thin film with higher face-on ratio than that of 12OD, but their unsuitable large-scale phase separation suppressed their efficient photocurrent generation, leading to poor PCE of 2–3%. However, the surface morphology of 12OD-2 and 8OD-2 blended films are drastically improved by increasing Mn, which leads to the enhancement of Jsc and higher PCE of up to 4.3%. However, high-Mn polymers 12OD-2 and 8OD-2 formed high-crystalline film with about 10–15% lower face-on ratio than that of high-Mn polymer 12OD, leading to poor hole transporting ability, and thus lower Jsc and PCE. From this result, too much strong intermolecular interaction promotes the formation of unsuitable edge-on orientation in blended films. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1757–1767.

DOI： 10.1002/pola.29058

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Nature Publishing Group  

The incorporation of a highly extended π-electron system into a polymer backbone is an effective strategy to develop high-performance donor–acceptor (D–A) polymers suitable for organic electronics because this strategy can facilitate a dense π-π stacking structure, leading to efficient carrier transport. With this in mind, we developed phenanthro[1,2-b:8,7-b′]dithiophene (PDT) because this new phenacene-type molecule has a highly crystalline nature, deep HOMO level, and high hole mobility, which are characteristics known to be suitable for a donor unit in high-performance D–A polymers. In this focus review, we report recent progress in PDT-containing D-A polymers combined with various strong acceptor units. Incorporation of PDT into a polymer backbone results in deep HOMO energy levels of −5.4~−5.5 eV, strong aggregation, and a dense packing structure with a short π-stacking distance of 3.5~3.6 Å. PDT-based polymers with appropriate alkyl side chains exhibit high hole mobilities of up to 0.18 cm2 V−1 s−1 in organic field-effect transistor (OFET) devices due to their tendency to form highly ordered edge-on structures. Furthermore, we can adjust their level of molecular orientation from edge-on to face-on by increasing their molecular weight, leading to a high power conversion efficiency of over 6% in polymer solar cell (PSC) applications. These results demonstrate that PDT is a good candidate as a high-performance building block in D-A polymers.

DOI： 10.1038/s41428-018-0072-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

Four bis[1]benzothieno[6,7-d:6′,7′-d′]benzo[1,2-b:4,5-b′]dithiophene (BBTBDT) derivatives bearing substituents on the molecular long axis were synthesized, and their transistor performance was evaluated. Among the obtained compounds, OFET devices based on the 2,9-diphenyl-substituted derivative (1d) on a β-PTS-modified Si/SiO2 substrate yielded the best morphological and crystalline structures, resulting in the highest hole mobility, as high as 0.16 cm2 V-1 s-1, and a low threshold voltage of -8 V. In the solid state, 1d formed a highly ordered and crystalline edge-on structure, which facilitated effective carrier transport. The detailed structure-property relationships were also disclosed by GIWAXS analysis, atomic force microscopy measurements, and theoretical calculations.

DOI： 10.1021/acs.joc.8b00483

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

Synthesis, characterization, and solar cell application of three 4,7-dialkylated phenanthro[1,2-b:8,7-b′]dithiophene (PDT)-difluorobenzothiadiazole (DFBT copolymers (P1-P3) with different linear alkyl side chains to improve solubility, molecular weight, and molecular orientation are described. The utilization of Ir-catalyzed direct borylation and sequential functionalization can selectively afford the target 4,7-dialkylated PDT as the monomers. Migita-Kosugi-Stille coupling in the presence of CuI can accelerate polymerization to afford high-molecular-weight polymers along with their improved solubility. The effect of alkyl substitution at the 4,7-positions on the electronic structure of PDT-DFBT copolymers is negligible. By installation of additional alkyl chains at the 4,7-positions of PDT, the synthesized polymers P1-P3 have lower intermolecular interaction than that of nonalkylated P0, but they still maintained aggregation behavior in solution. In addition, they formed a favorable face-on orientation with a short π-stacking distance of 3.6 Å, which can enhance their carrier transport ability, resulting in high Jsc and FF. As a result, their fabricated solar cells reached a PCE exceeding 6%, which are about 1.7-fold higher than that of P0. Comparison of alkyl side chain length at the 4,7-positions of PDT revealed that all polymers formed a predominantly face-on orientation and have a similar face-on ratio in blended films, but their crystallinity was decreased as the carbon chains at the 4,7-positions of PDT became shorter. On the other hand, the polymers with short alkyl side chains tended to have low surface roughness and small domain size of active layers, which is an ideal phase separation structure for high-performance PSCs. From these results, it could be seen that the polymers have a trade-off relationship between their domain size and crystallinity, but the impact of alkyl side chain length on their photovoltaic properties is rather small. Thus, the construction of face-on orientation is highly important to achieve a high PCE. Among three polymers, the P3/PC61BM-based solar cell with an optimal nanoscale phase separation structure with bicontinuous domain showed the highest PCE of up to 6.6%.

DOI： 10.1021/acs.macromol.7b02734

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Efficient syntheses of benzodithienofuran (BDTF; [1]benzothieno[3,2-b]thieno[2,3-d]furan) and benzodithienothiophene (BDTT; [1]benzothieno[3,2-b]thieno[2,3-d]thiophene) were achieved by the combination of an addition-elimination reaction, reduction, and Pd-catalyzed dehydrogenative cyclization. We also achieved the synthesis of pi-ex- tended BDTF and BDTT derivatives through the use of coupling reactions. The detailed physical properties of these compounds were investigated. The newly synthesized BDTFs exhibited strong fluorescence compared with BDTTs. 2,2'-Bis([1]benzothieno[3,2-b]thieno[2,3-d]furan) (BBTTF) exhibited p-type organic field-effect transistor (OFET) properties.

DOI： 10.1002/ajoc.201800270

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DOI： 10.1021/acs.macromol.8b01230

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

This paper reports the synthesis of D-A polymers containing 1,2-dithienylethene (DTE) units via palladium-catalyzed direct arylation polymerization (DArP). The reaction of dibromoisoindigo (1-Br) and DTE (2-H), in the presence of Pd2(dba)3·CHCl3 (0.5 mol%), P(2-MeOC6H4)3 (L1) (2 mol%), pivalic acid (1 equiv) as catalyst precursors, and Cs2CO3 (3 equiv) as a base affords poly(1-alt-2) with a high molecular weight (Mn up to 44,900). Although, it has been known that monomers, with plural C–H bonds, tend to form insoluble materials via direct arylation at undesirable C–H positions
the reaction of 1-Br and 2-H cleanly proceeds without insolubilization. The resulting polymer has a well-controlled structure and exhibits good charge transfer characteristics in an organic field-effect transistor (OFET), compared to the polymer produced by Migita–Kosugi–Stille cross-coupling polymerization. The DArP product displays an ideal linear relationship in the current–voltage curve, whereas the Migita–Kosugi–Stille product shows a VG-dependent change in the charge mobility.

DOI： 10.3390/molecules23040981

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Phenanthro[1,2-b:8,7-b']dithiophene (PDT)isoindigo (IID)-based polymers 12OD (L) and 12OD (H) with a different molecular weight were synthesized and characterized. By using further purified PDT and IID monomers, the high-molecular-weight polymer 12OD (H) with number-average molecular weight (M-n) over 50 kDa was obtained. Both 12OD (L) and 12OD (H) polymers have the same energy gap and highest occupied molecular orbital (HOMO) energy levels, indicating that the influence of molecular weight on their electronic structure is negligible, although 12OD (H) has stronger aggregation behavior than 12OD (L). 12OD (H)-based solar cells fabricated by using optimal solvent and additives showed an increased short-circuit current density (J(sc)) with same open-circuit voltage (V-oc) and fill factor (FF), resulting in a significantly improved power conversion efficiency (PCE) of up to 6.1%, which is approximately 70% higher than that of the 12OD (L)-based cell (3.5%). This result is due to the different molecular orientation caused by the higher molecular weight. Grazing incidence wide-angle X-ray scattering (GIWAXS) analyses revealed that the blended film of 12OD (H)/[6,6]-phenyl-C-61-butyric acid methyl ester (PC61BM) formed a face-on orientation with a long-range ordered structure, while a low crystalline edge-on structure was observed in the blended film of 12OD (L)/PC61BM. Such high crystalline and favorable molecular orientation could promote light harvesting efficiency and hole transporting ability, resulting in high J(sc) and thus an excellent PCE. From the detailed GIWAXS analysis, the orientation change of 12OD (H) was induced by the addition of PC61BM. This result suggests that the strong aggregation ability of 12OD (H) can drive crystallization and favors active interaction with PC61BM to form a face-on orientation. In this study, the increase in molecular weight can improve not only the thin-film structure such as crystallinity and phase separation structure but also the molecular orientation in the PDT-based polymer system.

DOI： 10.1021/acs.macromol.7b00778

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

Efficient synthesis and characterization of several piceno[4,3-b:9,10-b′]dithiophene (PiDT) derivatives by Negishi coupling, epoxidation, and Lewis acid-catalyzed cycloaromatization sequences and their potential utility in organic field-effect transistors (OFETs) have been reported. PiDT derivatives, with extended π-electron systems, showed high air stability due to their deep highest occupied molecular orbital energy levels (around -5.6 eV). OFET devices based on 2,11-dioctylated PiDT (C8-PiDT) showed excellent hole mobility, as high as 2.36 cm2 V-1 s-1. Their structure-property relationships were investigated by X-ray diffraction and atomic force microscopy.

DOI： 10.1021/acsomega.7b00015

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

We report the straightforward synthetic method and characterization of bis[1]benzothieno[2,3-d:2',3'-d']anthra[1,2-b:5,6-b']dithiophene (BBTADT) having nine aromatic rings fused without solubilizing groups. The highest mobility of fabricated OFETs utilizing BBTADT exhibited 2.7 x 10(-2) cm(2) V-1 s(-1) in polycrystalline films formed by vapor deposition, depending on the annealing temperatures of a substrate.

DOI： 10.1039/c6ra27455b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

A new phenacene-type molecule with five fused aromatic rings was synthesized: 2,7-didodecylphenanthro[2,1-b: 7,8-b'] dithiophene ((C12H25)(2)-i-PDT), with two terminal thiophene rings. Field-effect transistors (FETs) using thin films of this molecule were fabricated using various gate dielectrics, showing p-channel normally-off FET properties with field-effect mobilities (mu) greater than 1cm(2) V-1 s(-1). The highest mu value in the thin-film FETs fabricated in this study was 5.4 cm(2) V-1 s(-1), when a 150 nm-thick ZrO2 gate dielectric was used. This implies that (C12H25)(2)-i-PDT is very suitable for use in a transistor. Its good FET performance is fully discussed, based on electronic/topological properties and theoretical calculations.

DOI： 10.1038/srep38535

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

New PDT-based polymers were combined with two types of benzothiadiazole (BT) derivatives to improve their crystallinity and solar cell performance. These polymers show several advantages, including strong intermolecular interactions, deep HOMO energy levels, and a dense packing structure with a short pi-pi stacking distance of 3.5-3.6 angstrom. Combinations of PDT and BT units in polymers formed highly crystalline thin films with a long-range order, even in films blended with a fullerene derivative. This suggests that the introduction of optimal acceptor units may increase the regularity of the polymers, leading to effective pi-pi overlaps between the polymer backbones. However, although the present polymers also formed an appropriate phase separation structure in blended films, in fabricated solar cell devices they yielded low power conversion efficiencies (PCEs) not exceeding 3.8%. GI-WAXS analysis revealed that both polymers were present in a predominantly edge-on orientation. This unsuitable orientation for PSCs prevented efficient carrier transport and reduced charge collection efficiency, resulting in low J(sc) and thus low PCE. On the other hand, these polymers also formed highly oriented edge-on structures on n(+)-Si/SiO2 substrates, which are suitable for high-performance field-effect transistors (FETs), and a fabricated FET device showed a hole mobility as high as 0.18 cm(2) V-1 s(-1).

DOI： 10.1039/c5py01878a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Organic field-effect transistor (OFET) characteristics of phenanthrodithiophene (PDT)-isoindigo (IID) copolymers with different alkyl chains (12OD and BOBO) as an active layer, and their structure property relationships are described. The fabricated 12OD-based OFET device exhibited hole mobility of 0.16 cm(2)V(-1) s(-1). Grazing-incidence wide-angle X-ray scattering (GIWAXS) analysis revealed that 12OD formed highly ordered edge-on structure, whereas the BOBO film showed amorphous-like structure with no obvious pi-stacking crystallites. This may be attributed to a large steric hindrance of branched side chains in the BOBO polymer, which suppresses effective pi-pi overlaps between the adjacent polymer backbones.

DOI： 10.1246/cl.150357

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The synthesis;,characterization, and solar cell application of newly developed semiconducting polymers containing phenanthro[1,2-b:8,7-b']dithiophene (PDT) combined with A bis(thienyl)isoindigo (IID) unit are,described. The polymers with longer, alkyl Chains are sufficiently soluble to be compatible with the processes required to manufacture solar cells. In conventional solar cell, devices, polymers with all branched alkyl chains tend to form a higher proportion of a well-ordered face-on crystallite in the pi-stack direction than those with both linear and branched alkyl chains, which significantly improves the Ell factor (FF), resulting in higher power conversion efficiency (PCE). In terms of optimizing the alkyl chain lengths; the installation of longer alkyl side chains on the polymer backbone leads to low molecular weight polymer, which may promote a large phase separation. As a result, the polymers 12OD and BOBO, beating shorter alkyl groups, performed better, and a BOBO polymer-based solar cell (PSC) showed the best PCE value up to 3.83%. In the inverted PSCs, the polymers with all branched alkyl chains have a higher face-on ratio than those with both linear and branched alkyl chains. Because of their improved J(sc), inverted PSCs with BOBO/PC71BM gave the best performance, with a PCE up to 5.28%. Although an obvious dependence of photovoltaic properties on molecular order-was observed in conventional solar cell devices, no trend was observed in inverted cells, Possibly attributable to their amorphous nature, which arises from the axisymmetrical structure of PDT, leading to less effective pi-pi overlap and low crystallinity.

DOI： 10.1021/acs.macromol.5b00622

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Synthesis, characterization, and polymer solar cell and transistor application of a series of phenanthro[1,2-b:8,7-b]dithiophene-based donor-acceptor (D-A)-type semiconducting polymers combined with a diketopyrrolopyrrole unit are reported. The present polymers showed some unique features such as strong aggregation behavior, high thermal stability, and short - stacking distance (3.5-3.6 angstrom), which are suitable for high performance organic materials. In addition, they have a significantly extended absorption up to 1000 nm with a band gap of ca. 1.2 eV. However, such strong intermolecular interaction reduced their solubility and molecular weights, which resulted in low crystalline nature and moderate field-effect mobility of 0.01 cm(2) V-1 s(-1). Furthermore, such strong aggregation behavior led to the large-scale phase separation in the blend films, which may prevent the effective photocurrent generation, limiting J(sc) and power conversion efficiency of 2.0%. (c) 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 709-718

DOI： 10.1002/pola.27500

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHINESE CHEMICAL SOC  

A series of 3,10-dialkylated picenes has been synthesized from 3,10-dimethoxypicene through a divergent approach involving Ni-catalyzed alkynylation of a C-O bond, alkylation, and hydrogenation.

DOI： 10.1039/c5qo00039d

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DOI： 10.1039/c5tc90044a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A series of picenes having methoxy groups was synthesized through Pd-catalyzed Suzuki-Miyaura couplings or Wittig reaction/intramolecular cyclization sequences, and their physicochemical properties and single-crystal structures were evaluated. The substitution position effects between the outer 1,12-, 2,11-, and 4,9-position and the inner 3,10-position are quite different; the former showed the same electronic structure as that of picene, but the latter results in a HOMO geometry different from those of picene and other methoxy picenes. In addition, crystal structures of four types of methoxy-substituted picenes 4a-c,e strongly depend on their substitution position and number of methoxy groups, which dramatically changes the structures from the fully anisotropic 1D pi-stacked structure to a unique 3D herringbone structure due to steric hindrance of methoxy groups. The calculations of transfer integrals based on their single-crystal structures reveal that the methoxy picenes have intermolecular overlaps less effective than that of the parent nonsubstituted picene. These results are attributed not only to the packing structure but also to electronic structures such as the HOMO distribution. The preliminary OFET of the representative 4c,e showed hole mobilities significantly lower than that of picene due to their less effective intermolecular overlaps, as predicted by the calculated transfer integrals.

DOI： 10.1021/jo500543h

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

A compact surface potential based model for organic thin-film transistors (OTFTs), including both tail and deep trap states across the band gap, is reported. The model has been developed on the basis of a complete surface potential approach for undoped-body OTFTs. Accurate surface potentials are calculated by explicitly including the floating backside potential that varies with applied biases. A pseudo-2D resistor model is developed to capture the structural features of the OTFT. The resistor model considers, in particular, the effects originating from a bias dependent 2D current flow in the channel region and results in accurate reproduction of the electrical characteristics. The fitting capability of the developed OTFT model is verified against measured high-performance dinaphtho thieno thiophene (DNTT) based field-effect transistor data. Accurate reproduction of the current characteristics of the OTFT test structures is verified from a week to a strong inversion regime.

DOI： 10.1109/TSM.2014.2304736

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

We present new donor-acceptor semiconducting polymers based on a strong acceptor unit, thieno[3,2-b]thiophene-2,5-dione (TTD). The polymers exhibit a deep LUMO energy level of around -4 eV while preserving a relatively low-lying HOMO energy level of below -5 eV and a quite small optical band gap of 1.2 eV. Interestingly, bottom-gate-top-contact transistor devices based on the polymers demonstrate p-channel behavior with high hole-mobilites of 1.38 cm(2) V-1 s(-1), whereas top-gate-bottom-contact devices show ambipolar behavior with hole and electron mobilities of similar to 0.12 and similar to 0.20 cm(2) V-1 s(-1), respectively. These results indicate the great potential of TTD to be used as the building unit for high-performance semiconducting polymers.

DOI： 10.1039/c3tc32386b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

5,10-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)naphtho[1,2-c:5, 6-c′]bis[1,2,5]thiadiazole was successfully developed by the direct borylation reaction on the parent heterocycle and was utilized for the synthesis of naphtho[1,2-c:5,6-c′]bis[1,2,5]thiadiazole-based donor-acceptor copolymers. © 2013 The Royal Society of Chemistry.

DOI： 10.1039/c3py00161j

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

A series of substituted [6]phenacenes were synthesized through the Suzuki-Miyaura coupling and intramolecular double cyclization, using a polyhalobenzene and two different alkenylboronates. This methodology provides a direct route to unsymmetrical [6]phenacenes. The physicochemical properties of four [6]phenacenes were evaluated using UV-vis and fluorescence spectroscopies as well as cyclic voltammetry.

DOI： 10.1246/cl.130584

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A novel and versatile synthetic method for picene derivatives is developed using the Pd-catalyzed intramolecular double cyclization of the corresponding 2,3-bis[(1Z)-2-phenylethenyl]-1,4-dichlorobenzenes, which are readily prepared by Suzuki-Miyaura cross-coupling reactions of polyhalobenzenes with (Z)-arylethenylboronates. The physical properties of the obtained picenes can be modified via introducing a variety of functional groups to the picene frame-work All compounds are investigated by UV-vis and fluorescence spectroscopic measurements, CV, and DFT calculations as well as X-ray diffraction analysis.

DOI： 10.1021/ol401375n

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Organic photovoltaics based on 5-hexylthiophene-fused porphyrazines as the donor material were investigated. Bilayer solar cells consisting of a solution deposited donor layer and a vapor deposited C-60 acceptor layer showed decent photovoltaic performances of up to PCE of 1.2%, which is comparable to the corresponding CuPc/C-60 bilayer solar cells. On the other hand, bulk-heterojunction solar cells with PC61BM gave much reduced photovoltaic performances with maximum PCE of 0.70%, which can be ascribed to poor film morphology. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.orgel.2012.05.023

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Language：English   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/ja3015346

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Other Link： http://orcid.org/0000-0002-9302-5025

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We report the synthesis and characterization of a novel donor acceptor semiconducting polymer bearing naphtho-bisthiadiazole (NTz), a doubly benzothiadiazole (BTz)-fused ring, and its applications to organic field-effect transistors and bulk heterojunction solar cells. With NTz's highly pi-extended structure and strong electron affinity, the NTz-based polymer (PNTz4T) affords a smaller bandgap and a deeper HOMO level than the BTz-based polymer (PBTz4T). PNTz4T exhibits not only high field-effect mobilities of similar to 0.56 cm(2)/(V s) but also high photovoltaic properties with power conversion efficiencies of similar to 6.3%, both of which are significantly high compared to those for PBTz4T. This is most likely due to the more suitable electronic properties and, importantly, the more highly ordered structure of PNTz4T in the thin film than that of PBTz4T, which might originate in the different symmetry between the cores. NTz, with centrosymmetry, can lead to a more linear backbone in the present polymer system than BTz with wdsymmetry, which might be favorable for better molecular ordering. These results demonstrate great promise for using NTz as a bulding unit for high-performance semiconducting polymers for both transistors and solar cells.

DOI： 10.1021/ja210687r

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

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 give new insight into the structure-property relationships in BHJ solar cells.

DOI： 10.1002/adma.201103065

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

New linear-shaped naphtho[2,3-b:6,7-b']-difurans (NDFs) and -selenophenes (NDSs) were synthesized selectively from 3,7-dibromo-2,6-dihydroxynaphthalene and evaluated as organic semiconductors in comparison to corresponding naphtho[2,3-b:6,7-b']dithiophenes (NDTs). Evaluation of the electronic structures of the parent compounds by means of electrochemical and optical measurements clearly indicated that NDT and NDS are quite similar to each other, whereas only NDF has a marked different electronic structure. Thin film devices, including organic field-effect transistors (OFETs) and bilayer photovoltaics (OPVs) with C-60 or C-70 as an acceptor layer, were fabricated with the diphenyl derivatives using vacuum deposition. The thin films were found to be nicely crystalline with the edge-on molecular orientation both on Si/SiO2 (for OFETs) and ITO substrates (for OPVs). The thin films acted as active semiconducting layer in OFETs with mobility higher than 0.1 cm(2) V-1 s(-1) and as a donor layer in OPVs with power conversion efficiencies of up to 2.0%, indicating that the present naphthodichalcogenophenes are potential core structures for the development of new organic semiconductors.

DOI： 10.1021/cm202853b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

[2,20']Bi[naphtho[2,3-b] furanyl] was synthesized, characterized, and examined as an organic semiconductor for thin-film OFETs, bilayer OPVs, and organic light-emitting transistors (OLETs). In the devices, the material acted as a p-type semiconductor, showing moderately high mobility in OFETs, good photo conversion efficiency in OPVs, and blue-green emission in OLETs.

DOI： 10.1039/c2cc31960h

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Bilayer hetero-junction solar cells based on dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT) as the donor and C-60 as the acceptor were fabricated and evaluated. Although the bilayer thin film is almost transparent above 550 nm in the absorption spectra, relatively good solar cell performances [J(sc) = 3.96 (+/- 0.07) mAcm(-2), V-oc = 0.66 (+/- 0.01) V, FF = 0.64 (+/- 0.03), and eta = 1.70 (+/- 0.08) %] were achieved, indicating that efficient photocurrent generation at the DNTT/C-60 interface takes place. (C) 2011 The Japan Society of Applied Physics

DOI： 10.1143/APEX.4.061602

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Simple oligothiophene-based dyes with a cyanoacrylic acid anchor were synthesized and evaluated as a photosensitizer for dye-sensitized solar cells (DSSCs). Although the molecular properties of the dyes at a glance are quite similar to those of related oligothiophene dyes with a carboxylic acid anchor, the DSSC performance of the former (up to eta = 4.8%) is fairly improved over the latter (approximate to 1.2%). Absorption spectra of the oligothiophene dyes with the cyanoacrylic acid are red-shifted compared to those with the carboxylic acid, resulting in the improved photocurrent conversion efficiency at above 600 nm in the DSSCs. With the aid of theoretical calculations, electronic properties of the oligothiophene dyes were investigated, and it turned out that the excited states of the dyes are significantly affected by the anchoring groups. The cyanoacrylic acid anchor brings about a stabilized LUMO with localized electron density on the cyanoacrylic acid moiety, whereas the carboxylic acid dye has relatively a high-lying LUMO with delocalized electron density over the oligothiophene moiety. Thus, the difference in the DSSC performance is rationalized by the different electronic structure at the excited states caused by the anchoring groups on the oligothiophene cores.

DOI： 10.1246/bcsj.20100302

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

A series of alkylated dinaphtho[2,3-b:2&apos;,3&apos;-f]thieno[3,2-b]thiophenes (C-n-DNTTs) are developed as vapor-processable organic semiconductors for organic thin-film transistors (OTFTs). All the C-n-DNTT-based OTFTs showed typical p-channel FET characteristics and among them, C-10-DNTT, possessing two n-decyl groups, gave excellent FET characteristics under the ambient conditions with mobility close to 8.0 cm(2)V(-1)s(-1) and I-on/I-off &gt; 10(8).

DOI： 10.1002/adma.201001283

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/anie.201003609

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Introduction of diarylamino substituents on 2,7-diphenyl[1]-benzothieno[3,2-b]benzothiophene (DPh-BTBT) caused morphological change in the evaporated thin-film state: from highly crystalline films with edge-on molecular orientation for DPh-BTBT to amorphous films for the diarylamino derivatives. The former was unsuitable as a hole-transporting layer in organic light-emitting diodes (OLEDs), whereas the latter acted as a superior hole-transporting layer in multilayered OLEDs.

DOI： 10.1246/cl.2009.420

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

5-Hexylthiophene-fused porphyrazines were designed and synthesized as novel soluble phthalocyanine derivatives. Single-crystal X-ray structural analyses indicated that they have a well-ordered structure in the solid state in spite of the existence of disorder in the thiophene-fused porphyrazine core. Due to the high solubility and improved molecular ordering, the present 5-hexylthiophene-fused porphyrazines showed comparable performance to vapor-processable phthalocyanines as solution-processable organic semiconductors: solution-processed OFETs showed mobility of up to 0.2 cm(2) V(-1) s(-1).

DOI： 10.1039/b910824f

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Event date： 2022.3.22 - 2022.3.25

Language：Japanese   Presentation type：Oral presentation (general)  

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Event date： 2022.1.11 - 2022.1.12

Language：English   Presentation type：Oral presentation (invited, special)  

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Event date： 2021.9.7 - 2021.9.10

Language：Japanese   Presentation type：Poster presentation  

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Event date： 2021.3.16 - 2021.3.19

Language：Japanese   Presentation type：Oral presentation (general)  

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Event date： 2021.3.16 - 2021.3.19

Language：Japanese   Presentation type：Oral presentation (general)  

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Event date： 2020.11.5 - 2020.11.6

Language：Japanese   Presentation type：Oral presentation (invited, special)  

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Event date： 2020.9.16 - 2020.9.18

Language：Japanese   Presentation type：Oral presentation (general)  

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Event date： 2020.3

Language：Japanese   Presentation type：Oral presentation (general)  

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Event date： 2019.9.25 - 2019.9.27

Language：English   Presentation type：Oral presentation (invited, special)  

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Event date： 2019.3.9 - 2019.3.12

Language：Japanese   Presentation type：Oral presentation (general)  

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