Faculty Profiles - SUZUKI Atsushi

Papers - SUZUKI Atsushi

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Electronic structures and molecular dynamics of gadolinium-doped FAPbI3 perovskite crystals Reviewed

Atsushi Suzuki and Takeo Oku

Japanese Journal of Applied Physics 62 SK1006 2023.3

Additive effects of CuPcX<inf>4</inf>-TCNQ on CH<inf>3</inf>NH<inf>3</inf>PbI<inf>3</inf> perovskite solar cells Reviewed

Suzuki A., Hasegawa R., Funayama K., Oku T., Okita M., Fukunishi S., Tachikawa T., Hasegawa T.

Journal of Materials Science: Materials in Electronics 34 ( 7 ) 2023.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Materials Science: Materials in Electronics

Fabrication and characterization of methylammonium lead iodide CH3NH3PbI3 (MAPbI3) perovskite solar cells using decaphenylpentacyclosilane (DPPS), metal phthalocyanine complex doped with tetracyanoquinodimethane (TCNQ) as hole-transporting materials were performed. Additive effects of carboxylic acid, amino, or sulfonic acid sodium salt substituted phthalocyanine complex (MPcX4, M = Cu, Zn, Co, X = COOH, NH2 or SO3Na) doped with TCNQ on the photovoltaic properties, crystal orientation, morphologies and electronic structure were investigated. Incorporation of DPPS and CuPc(NH2)4 doped with TCNQ on the perovskite layer promoted the carrier generation and charge transfer, yielding the best performance of conversion efficiency as compared with other cases. The photovoltaic performance depended on the (100) crystal orientation in the perovskite layer. The surface modification and passivation in the perovskite layer supported the photovoltaic performance with stability under air atmosphere. The molecular interaction based on overlap of π-orbital on CuPc(NH2)4, TCNQ and the perovskite crystal promoted the charge transfer at the interface between the perovskite layer and hole-transporting layer, improving the photovoltaic performance.

DOI： 10.1007/s10854-023-10001-z

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Additive effects of CuPcX4-TCNQ on CH3NH3PbI3 perovskite solar cells Reviewed International journal

Atsushi Suzuki, Ryota Hasegawa, Kai Funayama, Takeo Oku, Masanobu Okita, Sakiko Fukunishi, Tomoharu Tachikawa, and Tomoya Hasegawa

J Mater Sci: Mater Electron 34 588 2023.2

Fabrication and Characterization of SnCl<inf>2</inf>- and CuBr-Added Perovskite Photovoltaic Devices Reviewed

Asakawa Y., Oku T., Kido M., Suzuki A., Okumura R., Okita M., Fukunishi S., Tachikawa T., Hasegawa T.

Technologies 10 ( 6 ) 2022.12

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

Perovskite photovoltaic devices added with tin (Sn) dichloride and copper (Cu) bromide were fabricated and characterized. The thin film devices were prepared by an ordinary spin-coating technique using an air blowing method in ambient air. A decaphenylcyclopentasilane layer was coated at the surface of perovskite layer and annealed at a high temperature of 190 °C. Conversion efficiencies and short-circuit current densities were improved for devices added with Sn and Cu compared with the standard devices. The energy gap of the perovskite crystal decreased through the Sn addition, which was also confirmed by first-principles calculations.

DOI： 10.3390/technologies10060112

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Ethylammonium Bromide- and Potassium-Added CH<inf>3</inf>NH<inf>3</inf>PbI<inf>3</inf> Perovskite Solar Cells Reviewed

Terada S., Oku T., Suzuki A., Okita M., Fukunishi S., Tachikawa T., Hasegawa T.

Photonics 9 ( 11 ) 2022.11

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

Perovskite solutions with added potassium iodide (KI) and ethylammonium bromide (EABr) were used to fabricate perovskite solar cells in ordinary air at 190 °C. The addition of EABr and KI induced (100)-oriented perovskite crystals, which resulted in the improvement in short-circuit current densities and conversion efficiencies. The short-circuit current density, open circuit voltage, and conversion efficiency of the best device were 21.0 mA cm−2, 0.942 V, and 12.88%, respectively. First-principles calculations also indicated a decrease in total energy per cell and an increase in energy gaps, which agreed with the improved results of device stabilities and photovoltaic properties.

DOI： 10.3390/photonics9110791

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Additive effect of lanthanide compounds into perovskite layer on photovoltaic properties and electronic structures Reviewed

Suzuki A., Kishimoto K., Oku T., Okita M., Fukunishi S., Tachikawa T.

Synthetic Metals 287 2022.7

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

Fabrication and characterization of lanthanide compound doped CH3NH3PbI3 (MAPbI3) perovskite solar cells have been performed for improving the photovoltaic properties with long-term stabilities of conversion efficiency. The purpose of this research is to investigate additive effect of formamidinium iodine (FAI) and lanthanide compound into the perovskite layer for improving carrier diffusion and mobility in the perovskite layer. Incorporation of FAI and europium chloride (EuCl2) into the perovskite crystals maintained the stability of conversion efficiency for 30 days. The photovoltaic properties were based on the crystal growth and orientation with suppression of decomposition, thermodynamic stabilities, and the narrow band dispersion with decrease of effective mass. In contrast case, addition of samarium or terbium compound reduced the stabilities, and suppressed the carrier mobility owing to the flat band dispersion of localized d orbital of samarium atom or 4 f orbital of terbium atom near valence band state. The annealing treatment improved the crystal orientation related to the carrier diffusion with inhibiting recombination, improving short circuit current density and external quantum efficiency. The perovskite crystal doped with EuCl2 and FAI have high advantage to apply for practical use of the photovoltaic devices with long-term stability.

DOI： 10.1016/j.synthmet.2022.117092

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Fabrication and Characterization of Perovskite Solar Cells Using Silicon Phthalocyanine Complex Reviewed International journal

Chihiro Ogawa, Iori Ono, Atsushi Suzuki, Takeo Oku, Masanobu Okita, Sakiko Fukunishi , Tomoharu Tachikawa and Tomoya Hasegawa

3rd International Online-Conference on Nanomaterials session Polymer Nanomaterials, Soft Nanomaterials, Nanocoatings/Thin films, and Nanostructured Surfaces 2022.4

Effects of Adding Alkali Metals and Organic Cations to Cu-Based Perovskite Solar Cells Reviewed

Okumura R., Oku T., Suzuki A., Okita M., Fukunishi S., Tachikawa T., Hasegawa T.

Applied Sciences (Switzerland) 12 ( 3 ) 2022.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Sciences (Switzerland)

First-principles electronic band calculations were used to investigate the effects of alkali metals and organic cations added to Cu-based perovskite solar cells. The copper d-orbital band was slightly above the valence-band maximum and functioned as an acceptor level for carrier genera-tion. Excitation from iodine p-orbitals and copper d-orbitals to alkali metal s-orbitals could suppress carrier recombination and promote carrier transport. Experimental solar conversion efficiencies increased after adding both Cu and Na, in agreement with the calculations. Total-energy calculations indicated that the perovskite crystal stability increased with the addition of ethyl ammonium, alt-hough the total energy decreased with the addition of Cu and Na.

DOI： 10.3390/app12031710

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Fabrication and characterization of CH3NH3PbI3 solar cells with added guanidinium and inserted with decaphenylpentasilane Reviewed

Ono I., Oku T., Suzuki A., Asakawa Y., Terada S., Okita M., Fukunishi S., Tachikawa T.

Japanese Journal of Applied Physics 61 ( SB ) 2022.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

In this work we investigated the effects of the addition of guanidinium [C(NH2)3; GA] on CH3NH3PbI3 perovskite solar cells fabricated at a high temperature of 190°C in atmospheric air. The addition of GA iodide and the insertion of decaphenylpentasilane between the perovskite and hole transport layer improved the external quantum efficiency and short-circuit current density, and the conversion efficiencies were stable after 1 month. X-ray diffraction showed that the lattice constant of the perovskite crystals was increased by the addition of GA, and addition of GA also improved the surface morphology. First-principles calculations on the density of states and band structures showed reduction of the total energy by the addition of GA and the effectiveness of the nitrogen atoms in GA.

DOI： 10.35848/1347-4065/ac2661

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Effects of copper addition to methylammonium/potassium- based perovskite solar cells Reviewed

Ayu Enomoto, Atsushi Suzuki, Takeo Oku, Masanobu Okita, Sakiko Fukunishi, Tomoharu Tachikawa and Tomoya Hasegawa

Chem. Proc. 9 ( 1 ) 2022.1

Effects of Cu, K and Guanidinium Addition to CH<inf>3</inf>NH<inf>3</inf>PbI<inf>3</inf> Perovskite Solar Cells Reviewed

Enomoto A., Suzuki A., Oku T., Okita M., Fukunishi S., Tachikawa T., Hasegawa T.

Journal of Electronic Materials 2022.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Electronic Materials

In this study, CH3NH3PbI3 perovskite solar cells with added copper (Cu) and potassium (K) or guanidinium (GA) were fabricated and characterized. The effects of the additives on the photovoltaic properties, morphology and crystalline structure were investigated, and the electronic structures and thermodynamic stabilities are discussed. The stability and conversion efficiency of the perovskite solar cell improved by incorporating Cu at the lead site and K or GA at the CH3NH3 organic cation site in the cubic crystal. Simultaneous addition of Cu and K to the perovskite crystal suppressed decomposition of the crystal by desorption of methylammonium (MA), which led to improvement of the stability of the photovoltaic device. After 28 days, the conversion efficiency of the device with co-added Cu and K was still 10.8%, whereas that of the standard device decreased to 10.1%.

DOI： 10.1007/s11664-022-09688-3

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Effects of polysilane addition to chlorobenzene and high temperature annealing on CH3NH3PBI3 perovskite photovoltaic devices Reviewed

Oku T., Taguchi M., Suzuki A., Kitagawa K., Asakawa Y., Yoshida S., Okita M., Minami S., Fukunishi S., Tachikawa T.

Coatings 11 ( 6 ) 2021.6

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

CH3NH3PbI3 perovskite photovoltaic devices treated with a polysilane layer were fabricated and characterized. Decaphenylcyclopentasilane (DPPS) in chlorobenzene solution was deposited at the surface of the perovskite layer, and the resulting device was annealed at 140-260 °C. The photoconversion efficiencies of the DPPS-treated device remained high even after 255 days in ambient air. Raman scattering spectroscopy and ab initio molecular orbital calculations of DPPS suggested that it increased hole transport efficiency in the treated devices, which was confirmed from the high shunt resistances of the DPPS-treated devices.

DOI： 10.3390/coatings11060665

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Effects of mixed-valence states of Eu-doped FAPbI3 perovskite crystals studied by first-principles calculation Reviewed International journal

A. Suzuki and T. Oku

Materials Advances 2 2609 - 2616 2021.3

Fabrication and Characterization of Ni-, Co-, and Rb-Incorporated CH3NH3PbI3 Perovskite Solar Cells Reviewed International journal

A. Suzuki, M. Oe and T. Oku

Journal of Electronic Materials 50 ( 4 ) 1980 - 1995 2021.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Electronic Materials Participation form：Joint(The main charge)

Ni- and Co-incorporated CH3NH3PbI3 perovskite solar cells were fabricated and characterized to optimize the photovoltaic and optical properties related to surface morphology, crystal growth and orientation, and electronic structures. Partially replacing Pb with Ni or Co in the perovskite crystals improved the photovoltaic performance and carrier mobility based on the effective mass in the band structure. In particular, the addition of both Ni and Rb compounds to perovskite improved the long-term stability of the photovoltaic cells, which depended on surface modification and coverage, crystal growth, and the high (100) orientation in the perovskite layer. The short-circuit current density of the cells was increased by promoting the generation and mobility of photoinduced carriers, which were inversely proportional to the effective mass ratio. Electron correlation was associated with the promotion of charge transfer owing to the hybridization between the 3d orbitals of Ni and the 5p orbitals of the I atoms near the valence band state.

DOI： 10.1007/s11664-021-08759-1

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Additive Effects of Guanidinium Iodide on CH3NH3PbI3 Perovskite Solar Cells Reviewed

Kishimoto T., Oku T., Suzuki A., Ueoka N.

Physica Status Solidi (A) Applications and Materials Science 2021.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Physica Status Solidi (A) Applications and Materials Science

CH3NH3PbI3 (MAPbI3) perovskite solar cells with guanidinium (C(NH2)3+, GA+) are fabricated at 150 °C using 3CH3NH3I:PbCl2 starting composition in ambient atmosphere, and characterized. Their photoconversion efficiencies and stabilities are improved by the addition of a small amount of GA+. Lattice volumes are increased by the addition of GA+, which confirms the occurrence of GA+ substitution at the CH3NH3 site. Energy gaps are decreased by the addition of GA+, which agrees well with the results of molecular orbital calculation and band calculation. The carrier trap density is reduced by the GA+ addition, which suggests that lattice defects are suppressed by the GA+ doping. Two-year stabilities of the devices in ordinary air are also investigated, which indicate the effectiveness of GA addition.

DOI： 10.1002/pssa.202100396

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Additive Effects of Copper and Alkali Metal Halides into Methylammonium Lead Iodide Perovskite Solar Cells Reviewed

Suzuki A., Kitagawa K., Oku T., Okita M., Fukunishi S., Tachikawa T.

Electronic Materials Letters 2021.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Electronic Materials Letters

Fabrication and characterization of methylammonium lead iodide perovskite solar cells incorporated with formamidinium iodide, copper halides, alkali metal halides and decaphenylcyclopentasilane were performed. Addition of CuCl and KI at 2% into the perovskite layer offered compact morphologies and crystal orientation in the perovskite layer, improving short circuit current densities, series resistance and open-circuit voltages related to conversion efficiencies. The stabilities of conversion efficiencies were improved for the perovskite layer incorporated with 2% CuCl and 2% NaI. The stabilities depended on the state of the surface morphologies and crystal orientation while suppressing decomposition reaction in the perovskite layer. The photovoltaic mechanisms were associated with promotion of carrier generation and diffusion in the crystalline layer. The electronic correlation was based on the charge transfer between 5p orbital of I ion and 3d orbital of Cu ion near valence band, promoting the carrier generation and diffusion related to the short circuit current densities. Graphical Abstract: [Figure not available: see fulltext.]

DOI： 10.1007/s13391-021-00325-5

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Additive effects of methyl ammonium bromide or formamidinium bromide in methylammonium lead iodide perovskite solar cells using decaphenylcyclopentasilane Reviewed

Suzuki A., Taguchi M., Oku T., Okita M., Minami S., Fukunishi S., Tachikawa T.

Journal of Materials Science: Materials in Electronics 2021.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Materials Science: Materials in Electronics

Fabrication and characterization of methylammonium lead iodide perovskite solar cells incorporated with methylammonium bromide (MABr), formamidinium bromide (FABr), and decaphenylcyclopentasilane (DPPS) were performed. Additive effect of MABr or FABr into the perovskite layers inserted with DPPS as hole-transporting layer was investigated. Addition of 5% MABr or FABr into the perovskite layer improved the short-circuit current density, shunt resistance, and open-circuit voltages, which depended on the uniform morphologies while suppressing defects and pinholes in the perovskite layer. The stabilities of the photovoltaic performance depended on the degree of incorporation of MABr or FABr with the DPPS layer, which suppressed decomposition in the perovskite layer.

DOI： 10.1007/s10854-021-07023-w

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Fabrication and Characterization of Ni-, Co-, and Rb-Incorporated CH<inf>3</inf>NH<inf>3</inf>PbI<inf>3</inf> Perovskite Solar Cells Reviewed

Suzuki A, Oe M, Oku T

Journal of Electronic Materials 2021.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Electronic Materials

© 2021, The Minerals, Metals & Materials Society. Ni- and Co-incorporated CH3NH3PbI3 perovskite solar cells were fabricated and characterized to optimize the photovoltaic and optical properties related to surface morphology, crystal growth and orientation, and electronic structures. Partially replacing Pb with Ni or Co in the perovskite crystals improved the photovoltaic performance and carrier mobility based on the effective mass in the band structure. In particular, the addition of both Ni and Rb compounds to perovskite improved the long-term stability of the photovoltaic cells, which depended on surface modification and coverage, crystal growth, and the high (100) orientation in the perovskite layer. The short-circuit current density of the cells was increased by promoting the generation and mobility of photoinduced carriers, which were inversely proportional to the effective mass ratio. Electron correlation was associated with the promotion of charge transfer owing to the hybridization between the 3d orbitals of Ni and the 5p orbitals of the I atoms near the valence band state.

DOI： 10.1007/s11664-021-08759-1

Polysilane-Inserted Methylammonium Lead Iodide Perovskite Solar Cells Doped with Formamidinium and Potassium Reviewed International journal

Takeo Oku, Satsuki Kandori, Masaya Taguchi, Atsushi Suzuki, Masanobu Okita, Satoshi Minami, Sakiko Fukunishi and Tomoharu Tachikawa

Energies 13 ( 4776 ) 1 - 11 2020.9

Polysilane-Inserted Methylammonium Lead Iodide Perovskite Solar Cells Doped with Formamidinium and Potassium Reviewed

Takeo Oku, Satsuki Kandori, Masaya Taguchi, Atsushi Suzuki, Masanobu Okita, Satoshi Minami, Sakiko Fukunishi, Tomoharu Tachikawa

Energies 13 ( 4776 ) 1 - 11 2020.9

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Papers - SUZUKI Atsushi