Faculty Profiles - MATSUO Yutaka

Papers - MATSUO Yutaka

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Carbon-sandwiched perovskite solar cell Reviewed

Namyoung Ahn, Il Jeon, Jungjin Yoon, Esko I. Kauppinen, Yutaka Matsuo, Shigeo Maruyama, Mansoo Choi

Journal of Materials Chemistry A Vol. 6 ( 4 ) page： 1382 - 1389 2018.1

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

Promising perovskite solar cell technology with soaring power conversion efficiencies has the common problems of low stability and high cost. This work provides a solution to these problems by employing a carbon sandwich structure, in which the fullerene bottom layer solves the stability issue and the carbon nanotube top electrode layer offers the merits of having high stability and being low-cost. Devices fabricated using different hole-transporting materials infiltrated into carbon nanotube networks were examined for their performance and stability under constant illumination in air. Polymeric hole-transporting layers show much higher stability when combined with carbon nanotubes due to their compact nature and stronger interaction with the carbon network. As a result, the encapsulated device showed high stability both in air and under light illumination, maintaining up to 80% of the initial efficiency after 2200 hours under actual operation conditions. Cost analysis also shows that using the polymeric hole-transporting materials in carbon nanotube films brings the fabrication cost down to less than 5.5% that of conventional devices. Our study proposes a promising cell structure toward highly stable and low-cost perovskite photovoltaic technologies for the future.

DOI： 10.1039/c7ta09174e

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A Helically-Twisted Ladder Based on 9,9'-Bifluorenylidene: Synthesis, Characterization, and Charge Transport Properties Reviewed

Jinjia Xu, Atsuro Takai, Alisa Bannaron, Takafumi Nakagawa, Yutaka Matsuo, Manabu Sugimoto, Yoshitaka Matsushita, Masayuki Takeuchi

Materials Chemistry Frontiers Vol. 2 page： 780 - 784 2018.1

A fluorenylidene-acridane that becomes dark in color upon grinding-ground state mechanochromism by conformational change Reviewed

Tsuyoshi Suzuki, Hiroshi Okada, Takafumi Nakagawa, Kazuki Komatsu, Chikako Fujimoto, Hiroyuki Kagi, Yutaka Matsuo

Chemical Science Vol. 9 ( 2 ) page： 475 - 482 2018.1

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

We report mechanochromic color change controlled by conformational change (between folded and twisted conformers) of fluorenylidene-acridanes (FAs). FAs with four N-alkyl groups (methyl, ethyl, n-butyl and n-octyl) were synthesized via the Barton-Kellogg reaction of diazofluorene and electrophilic N-tert-butoxy carbonyl thioacridone, deprotection of the tert-butoxy carbonyl group gives fluorenylacridine, and alkylation on the nitrogen atom is done using alkyl tosylate or triflate. FAs were characterized by NMR, UV-vis absorption and photoluminescence spectroscopy, theoretical calculation, cyclic voltammetry, and powder and single-crystal X-ray analyses. The color and folded/twisted conformation of the FAs were changed by the choice of substituent on the nitrogen atom, physical state (solution or solid), and morphology (crystalline or amorphous). Grinding of N-methyl FA solids, using an agate mortar, caused the morphology to change from a crystalline to amorphous state, which induced a conformational change from the folded to the twisted conformer, and a mechanochromic color change from yellow to dark green. The reverse color change, along with a morphological and conformational change to the folded conformer, was performed by solvent vapor exposure (chloroform). The twisted and folded conformers showed ambipolar (hole/electron) and hole-only transport properties, respectively.

DOI： 10.1039/c7sc03567e

Non-doped and unsorted single-walled carbon nanotubes as carrier-selective, transparent, and conductive electrode for perovskite solar cells Reviewed International coauthorship

Takahiro Sakaguchi, Il Jeon, Takaaki Chiba, Ahmed Shawky, Rong Xiang, Shohei Chiashi, Esko I. Kauppinen, Nam-Gyu Park, Yutaka Matsuo, Shigeo Maruyama

MRS Communications Vol. 8 ( 3 ) page： 1058 - 1063 2018

Substituent effects in magnesium tetraethynylporphyrin with two diketopyrrolopyrrole units for bulk heterojunction organic solar cells Reviewed

Ogumi Keisuke, Nakagawa Takafumi, Okada Hiroshi, Sakai Ryohei, Wang Huan, Matsuo Yutaka

JOURNAL OF MATERIALS CHEMISTRY A Vol. 5 ( 44 ) page： 23067 - 23077 2017.11

Comparative density functional theory-density functional tight binding study of fullerene derivatives: effects due to fullerene size, addends, and crystallinity on band structure, charge transport and optical properties Reviewed

Amrita Pal, Lai Kai Wen, Chia Yao Jun, Il Jeon, Yutaka Matsuo, Sergei Manzhos

PHYSICAL CHEMISTRY CHEMICAL PHYSICS Vol. 19 ( 41 ) page： 28330 - 28343 2017.11

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

We present a systematic comparative density functional theory-density functional tight binding study of multiple derivatives of C60 and C70 with different addends, in molecular as well as solid state. In particular, effects due to fullerene size, type and number of addends, and of crystallinity on band structure, charge transport, and optical properties are investigated. These are important, in particular, for rational selection of fullerene derivatives as acceptor and electron transport layers in organic as well as planar inverted perovskite solar cells. We find that by the choice of type and number of addends, one can modulate the LUMO within 0.4 eV. Changes in the HOMO can reach 0.7 eV. Substituting C70 for C60 results in destabilization of the HOMO by about 0.1 eV for indene and quinodimethane addends and by a less significant amount for PCBM addends. The effect of C70-C60 substitution on the LUMO is of similar magnitude. A more significant change in HOMO-LUMO energy is seen for the aryl addends. On the other hand, all C70 based molecules have strong visible absorption. For most addends, the crystal packing leads to a stabilization of both the LUMO and HOMO by about similar to 0.2 and similar to 0.1 eV, respectively, vs. single molecules. When using bis-addends, it is also possible to enhance the visible absorption. Electron and hole transport rates are computed to vary vastly depending on the addends chosen; specifically, we compute that indene and quimodimethane addends can enhance charge transport rates while the aryl addend is predicted to result in substantially smaller mobilities of electrons and holes, vs. PC60BM. Furthermore, the -CH2 and bisaddend addition can significantly enhance the charge transfer rates for the PCBM addend.

DOI： 10.1039/c7cp05290a

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Carbon Nanotubes versus Graphene as Flexible Transparent Electrodes in Inverted Perovskite Solar Cells Reviewed International coauthorship

Il Jeon, Jungjin Yoon, Namyoung Ahn, Mohamed Atwa, Clement Delacou, Anton Anisimov, Esko I. Kauppinen, Mansoo Choi, Shigeo Maruyama, Yutaka Matsuo

Journal of Physical Chemistry Letters Vol. 8 ( 21 ) page： 5395 - 5401 2017.11

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Transparent carbon electrodes, carbon nanotubes, and graphene were used as the bottom electrode in flexible inverted perovskite solar cells. Their photovoltaic performance and mechanical resilience were compared and analyzed using various techniques. Whereas a conventional inverted perovskite solar cells using indium tin oxide showed a power conversion efficiency of 17.8%, the carbon nanotube- and graphene-based cells showed efficiencies of 12.8% and 14.2%, respectively. An established MoO3 doping was used for carbon electrode-based devices. The difference in the photovoltaic performance between the carbon nanotube- and graphene-based cells was due to the difference in morphology and transmittance. Raman spectroscopy, and cyclic flexural testing revealed that the graphene-based cells were more susceptible to strain than the carbon nanotube-based cells, though the difference was marginal. Overall, despite higher performance, the transfer step for graphene has lower reproducibility. Thus, the development of better graphene transfer methods would help maximize the current capacity of graphene-based cells.

DOI： 10.1021/acs.jpclett.7b02229

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Perovskite Solar Cells Using Carbon Nanotubes Both as Cathode and as Anode Reviewed International coauthorship

Il Jeon, Seungju Seo, Yuta Sato, Clement Delacou, Anton Anisimov, Kazu Suenaga, Esko I. Kauppinen, Shigeo Maruyama, Yutaka Matsuo

JOURNAL OF PHYSICAL CHEMISTRY C Vol. 121 ( 46 ) page： 25743 - 25749 2017.11

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Organic-inorganic halide perovskite solar cells have received much attention because they achieve high power conversion efficiencies while providing the advantages of thin-film solar cells, namely, solution processability and potentially low fabrication costs. However, at the current level of halide perovskite solar cell technology, these advantages cannot be maximized because of structural and material limitations. Here, we provide a solution to these problems by replacing conventional metal and metal oxide electrodes with carbon nanotube electrodes. We also simplified the structure to achieve entirely solution-processable perovskite solar cells. Through this study, we demonstrate the function of carbon nanotubes as both the anode and the cathode in perovskite solar cells. Economic modeling suggests that this novel architecture reduces costs dramatically. This work realizes innovations in the materials, costs, and processing of inverted-type perovskite solar cells.

DOI： 10.1021/acs.jpcc.7b10334

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Synthesis and Crystal Structure of Li+@Fluoreno[60]fullerene: Effect of Encapsulated Lithium Ion on Electrochemistry of Spiroannelated Fullerene Reviewed International coauthorship

Hiroshi Ueno, Hiroshi Okada, Shinobu Aoyagi, Yutaka Matsuo

Journal of Organic Chemistry Vol. 82 page： 11631 - 11635 2017.10

Highly Conductive and Transparent Large-Area Bilayer Graphene Realized by MoCl5 Intercalation Reviewed

Hiroki Kinoshita, Il Jeon, Mina Maruyama, Kenji Kawahara, Yuri Terao, Dong Ding, Rika Matsumoto, Yutaka Matsuo, Susumu Okada, Hiroki Ago

Advanced Materials Vol. 29 ( 41 ) page： 1702141 2017.9

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

Bilayer graphene (BLG) comprises a 2D nanospace sandwiched by two parallel graphene sheets that can be used to intercalate molecules or ions for attaining novel functionalities. However, intercalation is mostly demonstrated with small, exfoliated graphene flakes. This study demonstrates intercalation of molybdenum chloride (MoCl5 ) into a large-area, uniform BLG sheet, which is grown by chemical vapor deposition (CVD). This study reveals that the degree of MoCl5 intercalation strongly depends on the stacking order of the graphene; twist-stacked graphene shows a much higher degree of intercalation than AB-stacked. Density functional theory calculations suggest that weak interlayer coupling in the twist-stacked graphene contributes to the effective intercalation. By selectively synthesizing twist-rich BLG films through control of the CVD conditions, low sheet resistance (83 Ω ▫(-1) ) is realized after MoCl5 intercalation, while maintaining high optical transmittance (≈95%). The low sheet resistance state is relatively stable in air for more than three months. Furthermore, the intercalated BLG film is applied to organic solar cells, realizing a high power conversion efficiency.

DOI： 10.1002/adma.201702141

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Regiocontrolled Electrosynthesis of [60]Fullerene Bisadducts: Photovoltaic Performance and Crystal Structures of C-60 o-Quinodimethane Bisadducts Reviewed International coauthorship

Zong-Jun Li, Sisi Wang, Shu-Hui Li, Tao Sun, Wei-Wei Yang, Kazutaka Shoyama, Takafumi Nakagawa, Il Jeon, Xiaoniu Yang, Yutaka Matsuo, Xiang Gao

JOURNAL OF ORGANIC CHEMISTRY Vol. 82 ( 16 ) page： 8676 - 8685 2017.8

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

C-60 o-quinodimethane bisadducts [C-60(QM)(2)] are promising electron acceptors for bulk heterojuction (BHJ) organic solar cells (OSCs). However, previous production of C-60(QM)(2) often resulted in excessive regioisomers, which were difficult to purify and might consequently obscure the structure performance study of the organofullerene acceptors. Herein, the electrosynthesis of C-60(QM)(2) is reported. The reaction exhibits a strong regiocontrol with generation of fewer regioisomers. Pure regioisomers of cis-2, trans-3, and e C-60(QM)(2) are obtained, and the structures are solved with single-crystal X-ray diffraction. Interestingly, the cis-2 and trans-3 regioisomers exhibit better photovoltaic performance than the e regioisomer in the OSCs based on poly(3-hexylthiophene) (P3HT), which can be correlated with their structural difference.

DOI： 10.1021/acs.joc.7b01732

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Crystallographic Structure Determination of Both [5,6]- and [6,6] Isomers of Lithium-Ion-Containing Diphenylmethano[60]fullerene Reviewed

Hiroshi Okada, Hiroki Kawakami, Shinobu Aoyagi, Yutaka Matsuo

JOURNAL OF ORGANIC CHEMISTRY Vol. 82 ( 11 ) page： 5868 - 5872 2017.6

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

Organic functionalization of lithium-ion-containing [60]fullerene, Li+@C-60, was performed by using diphenyl(diazo)methane as a stable, readily available diazo compound to obtain lithium-ion-containing [5,6]- and [6,6]-diphenylmethano[60]fullerenes, Li+@C61Ph2. The bis(trifluoromethanesulfonyl)imide (TFSI) salts of [5,6]- and [6,6]-Li+@C61Ph2 were successfully separated by using a cation exchange column with eluent containing LiTFSI. Improved separation protocol and high crystallinity of ionic components in less polar solvents enabled separate crystallization of each isomer. Both [5,6]-open and [6,6]-closed structures of Li+@C61Ph2 were determined by synchrotron radiation X-ray crystallography. Elucidating the [5,6] -open methano[60]fullerene (fulleroid) structure will contribute to materials research on fulleroids.

DOI： 10.1021/acs.joc.7b00730

Scalable and Solid-state Redox Functionalization of Transparent Single-walled Carbon Nanotube Films for Highly Efficient and Stable Solar Cells Reviewed International coauthorship

Kehang Cui, Yang Qian, Il Jeon, Anton Anisimov, Yutaka Matsuo, Esko I. Kauppinen, Shigeo Maruyama

Advanced Energy Materials Vol. 7 page： 1700449 2017.5

Dual Interfacial Modifications Enable High Performance Semitransparent Perovskite Solar Cells with Large Open Circuit Voltage and Fill Factor Reviewed

Qifan Xue, Yang Bai, Meiyue Liu, Ruoxi Xia, Zhicheng Hu, Ziming Chen, Xiao-Fang Jiang, Fei Huang, Shihe Yang, Yutaka Matsuo, Hin-Lap Yip, Yong Cao

ADVANCED ENERGY MATERIALS Vol. 7 ( 9 ) 2017.5

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

In this work, both anode and cathode interfaces of p-i-n CH3NH3PbI3 perovskite solar cells (PVSCs) are simultaneously modified to achieve large open-circuit voltage (V-oc) and fill factor (FF) for high performance semitransparent PVSCs (ST-PVSCs). At the anode, modified NiO serves as an efficient hole transport layer with appropriate surface property to promote the formation of smooth perovskite film with high coverage. At the cathode, a fullerene bisadduct, C-60(CH2)(Ind), with a shallow lowest unoccupied molecular orbital level, is introduced to replace the commonly used phenyl-C-61-butyric acid methyl ester (PCBM) as an alternative electron transport layer in PVSCs for better energy level matching with the conduction band of the perovskite layer. Therefore, the V-oc, FF and power conversion efficiency (PCE) of the PVSCs increase from 1.05 V, 0.74 and 16.2% to 1.13 V, 0.80 and 18.1% when the PCBM is replaced by C-60(CH2)(Ind). With the advantages of high V-oc and FF, ST-PVSCs are also fabricated using an ultrathin transparent Ag as cathode, showing an encouraging PCEs of 12.6% with corresponding average visible transmittance (AVT) over 20%. These are the highest PCEs reported for ST-PVSCs with similar AVTs paving the way for using ST-PVSCs as power generating windows.

DOI： 10.1002/aenm.201602333

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Indium Tin Oxide-free Small Molecule Organic Solar Cells Using Single-walled Carbon Nanotube Electrodes Reviewed International coauthorship

Clément Delacou, Il Jeon, Seungju Seo, Takafumi Nakagawa, Esko I. Kauppinen, Shigeo Maruyama, Yutaka Matsuo

ECS Journal of Solid State Science and Technology Vol. 6 ( 6 ) page： M3181 - M3184 2017.5

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Electrochemical Society Inc.

We demonstrated single-walled carbon nanotubes (SWNTs) electrode-based small molecule organic solar cells (OSCs) using diketopyrrolopyrrole donor, DPP(TBFu)2 as an electron donor with [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as an electron acceptor. SWNT films with 60% transmittance (at 550 nm) were dry-transferred onto glass substrates to replace conventional indium tin oxide (ITO) electrodes. In order to improve the conductivity of the SWNT electrodes, MoOx thermal doping was applied followed by spin coating of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) to enhance doping and electrode blocking function. The indium-free devices showed a power conversion efficiency (PCE) of 1.00% while ITO-based devices showed a PCE of 3.79%.

DOI： 10.1149/2.0311706jss

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Regioselective acylation and carboxylation of [60] fulleroindoline via electrochemical synthesis Reviewed

Hao-Sheng Lin, Yutaka Matsuo, Jun-Jie Wang, Guan-Wu Wang

ORGANIC CHEMISTRY FRONTIERS Vol. 4 ( 4 ) page： 603 - 607 2017.4

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

A regioselective and highly efficient electrochemical method for direct acylation and carboxylation of a [60] fulleroindoline has been developed. By using inexpensive and readily available acyl chlorides and chloroformates, both keto and ester groups can be easily attached onto the fullerene skeleton to afford 1,2,3,16-functionalized [60] fullerene derivatives regioselectively. In addition, a plausible mechanism for the formation of fullerenyl ketones and esters is proposed, and their further transformations under basic and acidic conditions have been investigated.

DOI： 10.1039/c6qo00654j

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Structures and properties of Saturn-like complexes composed of oligothiophene macrocycle with methano[60]fullerene and [70]fullerene Reviewed

Iyoda Masahiko, Shimizu Hideyuki, Aoyagi Shinobu, Okada Hiroshi, Zhou Biao, Matsuo Yutaka

CANADIAN JOURNAL OF CHEMISTRY Vol. 95 ( 3 ) page： 315 - 319 2017.3

An efficient organic solvent-free solution-processing strategy for high-mobility metal chalcogenide film growth Reviewed

Jie Zhao, Il Jeon, Qinghua Yi, Menka Jain, Mark H. Rummeli, Pingyuan Song, Yutaka Matsuo, Guifu Zou

GREEN CHEMISTRY Vol. 19 ( 4 ) page： 946 - 951 2017.2

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

One of the primary challenges for high-quality metal chalcogenide film growth by a chemical solution approach is to avoid the use of volatile/hazardous organic solvents during the fabrication processes. Herein, we demonstrate an organic solvent-free solution processing method which has the ability to enable growth of a diverse range of metal chalcogenide films. The processing solution is prepared by combining the required metal ions with non-volatile and non-flammable ionic liquid precursor solutions. These stable and homogeneous solutions can form a variety of high-quality and uniform metal chalcogenide films. Due to the facile and instant control of the stoichiometry used in this method, the band gap of multi-element compound semiconductors, for example quinary Cu2ZnSn( S, Se) (4), can be easily tuned from 1.01 eV of Cu2ZnSnSe4 to 1.52 eV of Cu2ZnSnS4. The resulting film also shows high hole mobility with a maximum of 56.9 cm(2) V-1 s(-1) for a carrier concentration of 3.24 x 10(16) cm(-3) at room temperature. Cu2ZnSnS4-based solar cells displayed an efficiency of 5.68%, which is comparable to the reported efficiencies of solar cells prepared by methods involving organic solvents ( 5.0-6.4%).

DOI： 10.1039/c6gc02489k

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Polymer-Fullerene Solar Cells Reviewed

Il Jeon, Yutaka Matsuo

Encyclopedia of Polymer Science and Technology page： 1 - 17 2017.2

Fullerene cation-mediated demethylation/cyclization to give 5-and 7-membered cyclo[60] fullerene derivatives Reviewed

Yutaka Matsuo, Keisuke Ogumi, Ying Zhang, Hiroshi Okada, Takafumi Nakagawa, Hiroshi Ueno, Akiko Gocho, Eiichi Nakamura

JOURNAL OF MATERIALS CHEMISTRY A Vol. 5 ( 6 ) page： 2774 - 2783 2017.2

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

Single-bonded fullerene dimers, (C60R)(2) (R = (2-methoxyphenyl)dimethylsilylmethyl, (isopropoxy) dimethylsilylmethyl, and 2-methoxy-5-methylphenyl), afforded fullerene derivative cations (RC60+) in the presence of an oxidant (I-2, CuCl2, or CuBr2), leading to 5- and 7-membered cyclo[60]fullerene derivatives such as cyclo[60]fullerenes containing a Si-O bond, cyclo[60]fullerenes containing a C-60-O bond, and dihydrobenzofurano[60]fullerene. The reaction mechanism involved thermal homolytic cleavage to give fullerene radicals, oxidation of the radicals to generate fullerene cations, and then demethylative cyclization in which the fullerene cationic centers interact with an aromatic group or the oxygen atoms of methoxy groups to produce the cyclized products. The obtained cyclo[60]fullerene derivatives were used in bulk-heterojunction organic solar cells and showed moderate power conversion efficiency and respectable open-circuit voltage.

DOI： 10.1039/c6ta10319g

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