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ISHIKAWA Ryo
| Mathematics, Electronics and Informatics Division | Assistant Professor |
| Department of Electrical Engineering,Electronics, and Applied Physics |
Performance information
■ Paper- Fabrication of efficient methylammonium-free perovskite thin-film solar cells without post-treatment and antisolvent
Ryo Ishikawa
Next Materials, Volume：6, First page：100283, Last page：100283, Jan. 2025, [Reviewed], [Lead, Corresponding]
Elsevier BV, Scientific journal
DOI：https://doi.org/10.1016/j.nxmate.2024.100283
DOI ID：10.1016/j.nxmate.2024.100283, ISSN：2949-8228 - Inverted-Structured Perovskite Solar Cells with a TiO2 Electron-Collector Layer Formed at Room Temperature from Titanium Halide Solutions
Atsushi Kogo; Ryo Ishikawa; Takurou N. Murakami
ACS Applied Energy Materials, Sep. 2024, [Reviewed]
American Chemical Society (ACS), Scientific journal
DOI：https://doi.org/10.1021/acsaem.4c01226
DOI ID：10.1021/acsaem.4c01226, ISSN：2574-0962, eISSN：2574-0962 - Polyelectrolyte-assisted uniform electron transporting layer on texture substrate for perovskite solar cells
Ryo Ishikawa
Chemistry Letters, Aug. 2024, [Reviewed], [Lead, Corresponding]
Abstract
Organic-inorganic halide perovskite solar cells using textured transparent conductive films exhibit high efficiencies with improved short-circuit current density. However, uniform electron transport layer (ETL) deposition on textures by solution process is challenging. In this study, uniform ETL were formed by sequentially spin-coating polyelectrolyte with positively and negatively charged segments and negative SnO2 colloids solution and electrostatically enhancing the SnO2 coverage. The stabilized power output (SPO) was improved from 12.9% to 18.6% by incorporating this polyelectrolyte/SnO2 bilayer.
Oxford University Press (OUP), Scientific journal
DOI：https://doi.org/10.1093/chemle/upae158
DOI ID：10.1093/chemle/upae158, ISSN：0366-7022, eISSN：1348-0715 - Coherent optical response driven by non-equilibrium electron–phonon dynamics in a layered transition-metal dichalcogenide
Takumi Fukuda; Kotaro Makino; Yuta Saito; Paul Fons; Atsushi Ando; Takuya Mori; Ryo Ishikawa; Keiji Ueno; Jessica Afalla; Muneaki Hase
APL Materials, Volume：12, Number：2, Feb. 2024, [Reviewed]
Layered transition-metal dichalcogenides (TMDs) are model systems to explore ultrafast many-body interactions and various nonlinear optical phenomena. For the application of TMD-based optoelectronic devices capable of ultrafast response, it is essential to understand how characteristic electron–hole and electron–phonon couplings modify ultrafast electronic and optical properties under photoexcitation. Here, we investigate the sub-picosecond optical responses of layered semiconductor 2H–MoTe2 in the presence of an electron–hole (e–h) plasma and a long-lived coherent phonon. Transient reflectivity measurements depending on photon energy reveal that the optical response for short-time delays (< 1ps) was significantly modified by band-gap renormalization and state filling due to the presence of the e–h plasma. Furthermore, octave, sum, and difference phonon frequencies transiently appeared for the early time delays (< 2ps). The emergent multiple phonon frequencies can be described as higher-order optical modulations due to deformation-potential electron–phonon coupling under resonant photoexcitation conditions. This work provides comprehensive insights into fundamental physics and the application of non-equilibrium quasiparticle generations on TMDs under time-periodic phonon driving forces.
AIP Publishing, Scientific journal
DOI：https://doi.org/10.1063/5.0188537
DOI ID：10.1063/5.0188537, eISSN：2166-532X - Ultrafast melting of charge-density wave fluctuations at room temperature in 1T-TiSe2 monitored under non-equilibrium conditions
Yu Mizukoshi; Takumi Fukuda; Yuta Komori; Ryo Ishikawa; Keiji Ueno; Muneaki Hase
Applied Physics Letters, Volume：122, Number：24, Jun. 2023, [Reviewed]
We investigate the ultrafast lattice dynamics in 1T-TiSe2 using femtosecond reflection pump–probe and pump–pump–probe techniques at room temperature. The time-domain signals and Fourier-transformed spectra show the A1g phonon mode at 5.9 THz. Moreover, we observe an additional mode at ≈ 3 THz, corresponding to the charge-density wave (CDW) amplitude mode (AM), which is generally visible below Tc≈200 K. We argue that the emergence of the CDW amplitude mode at room temperature can be a consequence of fluctuations of order parameters based on the additional experiment using the pump–pump–probe technique, which exhibited suppression of the AM signal within the ultrafast timescale of ∼0.5 ps.
AIP Publishing, Scientific journal
DOI：https://doi.org/10.1063/5.0153161
DOI ID：10.1063/5.0153161, ISSN：0003-6951, eISSN：1077-3118 - State-of-the-Art of Solution-Processed Crystalline Silicon/Organic Heterojunction Solar Cells: Challenges and Future
Jaker Hossain; A. T. M. Saiful Islam; Koji Kasahara; Ryo Ishikawa; Keiji Ueno; Hajime Shirai
Challenges and Advances in Computational Chemistry and Physics, First page：33, Last page：56, May 2021
Springer International Publishing, In book
DOI：https://doi.org/10.1007/978-3-030-69445-6_2
DOI ID：10.1007/978-3-030-69445-6_2, ISSN：2542-4491, eISSN：2542-4483, SCOPUS ID：85105977440 - Solution-processed TiO2 as a hole blocking layer in PEDOT:PSS/n-Si heterojunction solar cells
Md. Enamul Karim; A.T.M. Saiful Islam; Yuki Nasuno; Abdul Kuddus; Ryo Ishikawa; Hajime Shirai
EPJ Photovoltaics, Volume：11, First page：7, Last page：7, Jul. 2020, [Reviewed]
The junction properties at the solution-processed titanium dioxide (TiO2)/n-type crystalline Si(n-Si) interface were studied for poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/n-Si heterojunction solar cells by the steady-state photovoltaic performance and transient reverse recovery characterizations. The power conversion efficiency could be increased from 11.23% to 13.08% by adjusting the layer thickness of TiO2 together with increasing open-circuit voltage and suppressed dark saturation current density. These findings originate from the enhancement of the carrier collection efficiency at the n-Si/cathode interface. The transient reverse recovery characterization revealed that the surface recombination velocity S was ∼375 cm/s for double TiO2 interlayer of ∼2 nm thickness. This value was almost the same as that determined by microwave photoconductance decay measurement. These findings suggest that solution-processed TiO2 has potential as a hole blocking layer for the crystalline Si photovoltaics.
EDP Sciences, Scientific journal
DOI：https://doi.org/10.1051/epjpv/2020004
DOI ID：10.1051/epjpv/2020004, eISSN：2105-0716 - Effect of thermally annealed atomic-layer-deposited AlOx/chemical tunnel oxide stack layer at the PEDOT:PSS/n-type Si interface to improve its junction quality
Md Enamul Karim; Yuki Nasuno; Abdul Kuddus; Tomofumi Ukai; Shunji Kurosu; Masahide Tokuda; Yasuhiko Fujii; Tatsuro Hanajiri; Ryo Ishikawa; Keiji Ueno; Hajime Shirai
JOURNAL OF APPLIED PHYSICS, Volume：128, Number：4, Jul. 2020, [Reviewed]
We investigated the effects of thermal annealing on an atomic layer deposition-fabricated AlOx/chemical tunnel oxide (ch-SiOx) stack layer, for passivating and enhancing the field-inversion at the poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/n-type crystalline Si (n-Si) interface. Annealing in N-2/H-2 forming gas at 560 degrees C for 30min increased the effective minority carrier lifetime (tau(eff)) of the AlOx/ch-SiOx stack layer to 300-331 mu s, which decreased sheet resistance and enhanced the built-in potential and open-circuit voltage in PEDOT:PSS/n-Si heterojunction solar cells to 750mV and 645mV, respectively. These improvements originate from the local chemical bond configuration of the tunnel oxide ch-SiOx, which determines the passivation ability and band alignment at the AlOx/n-Si interface.
AMER INST PHYSICS, English, Scientific journal
DOI：https://doi.org/10.1063/5.0007918
DOI ID：10.1063/5.0007918, ISSN：0021-8979, eISSN：1089-7550, Web of Science ID：WOS:000556325800003 - Synthesis of AlOx thin films by atmospheric-pressure mist chemical vapor deposition for surface passivation and electrical insulator layers
Arifuzzaman Rajib; Karim Md Enamul; Shunji Kurosu; Tomofumi Ukai; Masahide Tokuda; Yasuhiko Fujii; Tatsuro Hanajiri; Ryo Ishikawa; Keiji Ueno; Hajime Shirai
Journal of Vacuum Science & Technology A, Volume：38, Number：3, First page：033413, Last page：033413, May 2020
American Vacuum Society, Scientific journal
DOI：https://doi.org/10.1116/1.5143273
DOI ID：10.1116/1.5143273, ISSN：0734-2101, eISSN：1520-8559 - Improved efficiency of methylammonium-free perovskite thin film solar cells by fluorinated ammonium iodide treatment
Ryo Ishikawa; Keiji Ueno; Hajime Shirai
Organic Electronics, Volume：78, First page：105596, Last page：105596, Mar. 2020, [Reviewed], [Lead, Corresponding]
Elsevier BV, Scientific journal
DOI：https://doi.org/10.1016/j.orgel.2019.105596
DOI ID：10.1016/j.orgel.2019.105596, ISSN：1566-1199, ORCID：66687394 - Self-assembled Fluorinated Polymer Passivation Layer for Efficient Perovskite Thin-film Solar Cells
Yuma Moriya; Ryo Ishikawa; Shuhei Akiyama; Keiji Ueno; Hajime Shirai
Chemistry Letters, Volume：49, Number：1, First page：87, Last page：90, Jan. 2020, [Reviewed], [Corresponding]
Oxford University Press (OUP), Scientific journal
DOI：https://doi.org/10.1246/cl.190692
DOI ID：10.1246/cl.190692, ISSN：0366-7022, eISSN：1348-0715, ORCID：65263763 - Role of the solvent in large crystal grain growth of inorganic-organic halide FA0.8Cs0.2PbIxBr3 − x perovskite thin films monitored by ellipsometry
Koki Kawamura; Ryo Ishikawa; Yoko Wasai; Nataliya Nabatova-Gabain; Shun-ji Kurosu; Tomofumi Ukai; Masahide Tokuda; Yasuhiko Fujii; Tatsuro Hanajiri; Keiji Ueno; Hajime Shirai
Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, Volume：37, Number：6, First page：062401, Last page：062401, Oct. 2019, [Reviewed]
The role of an additional solvent thiosemicarbazide (TSC) in the synthesis of a highly crystallized inorganic–organic halide FA0.8Cs0.2PbIxBr3 − x perovskite using the co-solvent N,N-dimethylformamide/1-cyclohexyl-2-pyrrolidone has been investigated. Ellipsometry combined with x-ray diffraction and FTIR spectroscopy was used for characterization purposes. The average crystal grain size increased from several hundred nanometers to 1–1.5 μm with increasing content of TSC in the co-solvent. Ellipsometry and FTIR spectroscopy revealed that the as-deposited perovskite film before thermal annealing was distorted and featured a large number of voids; also, the Pb ions formed complexes with the C˭S groups in TSC, which suppressed the excessive nucleation. Removal of the co-solvent at the thermal annealing stage facilitated the rearrangement of the [Pb(IxBr3 − x)6]4− octahedral structure from a zero-dimensional to a three-dimensional network, which enhanced crystal grain growth.
American Vacuum Society, Scientific journal
DOI：https://doi.org/10.1116/1.5123399
DOI ID：10.1116/1.5123399, ISSN：2166-2746, eISSN：2166-2754, ORCID：65263772 - Highly crystalline large-grained perovskite films using two additives without an antisolvent for high-efficiency solar cells
Ryo Ishikawa; Keiji Ueno; Hajime Shirai
Thin Solid Films, Volume：679, First page：27, Last page：34, Jun. 2019, [Reviewed], [Lead, Corresponding]
Elsevier BV, Scientific journal
DOI：https://doi.org/10.1016/j.tsf.2019.03.030
DOI ID：10.1016/j.tsf.2019.03.030, ISSN：0040-6090, ORCID：65263783 - Thiocyanate Containing Two-Dimensional Cesium Lead Iodide Perovskite, Cs2PbI2(SCN)(2): Characterization, Photovoltaic Application, and Degradation Mechanism
Youhei Numata; Yoshitaka Sanehira; Ryo Ishikawa; Hajime Shirai; Tsutomu Miyasaka
ACS APPLIED MATERIALS & INTERFACES, Volume：10, Number：49, First page：42363, Last page：42371, Dec. 2018, [Reviewed]
We explored thiocyanate (SCN)-based two-dimensional (2D) organometal lead halide perovskite families toward photovoltaic applications. Using an SCN axial ligand and various cation species, we examined AA'PbI2(SCN)(2)-type 2D perovskite by replacing the cation species (AA') between methylammonium (MA), formamidinium (FA), and cesium. Among various cation compositions, only all-inorganic cesium-based SCN perovskite, Cs2PbI2(SCN)(2), film showed high thermal stability compared to known 2D perovskites. Perovskite solar cells (PSCs) using the Cs2PbI2(SCN)(2) absorber yielded approximately 2% conversion efficiency on the mesoscopic device. Relatively low efficiency is attributed, in addition to optical properties (large band gap (2.05 eV) and exciton absorption), to the orientation of perovskite layer parallel to the layered structure, preventing carrier extraction from the light-absorber perovskite. In device stability, the Cs-based 2D perovskite was stable against oxygen (oxidation), whereas it was found to be unstable against humidity. X-ray diffraction and X-ray photoelectron spectroscopy measurements showed that, unlike long alkylammonium-based 2D perovskite families such as BA(2)PbI(4) (BA = butylammonium), the Cs-based 2D perovskite can undergo hydrolysis due to the hydrophilic Cs cations.
AMER CHEMICAL SOC, English, Scientific journal
DOI：https://doi.org/10.1021/acsami.8b15578
DOI ID：10.1021/acsami.8b15578, ISSN：1944-8244, eISSN：1944-8252, Web of Science ID：WOS:000453488900057 - Fabrication of [CH(NH2)2]0.8Cs0.2PbI3 Perovskite Thin Films for n-i-p Planar-structure Solar Cells by a One-step Method Using 1-Cyclohexyl-2-pyrrolidone as an Additive
Ryo Ishikawa; Keiji Ueno; Hajime Shirai
Chemistry Letters, Volume：47, Number：7, First page：905, Last page：908, Jul. 2018, [Reviewed], [Lead, Corresponding]
Oxford University Press (OUP), Scientific journal
DOI：https://doi.org/10.1246/cl.180216
DOI ID：10.1246/cl.180216, ISSN：0366-7022, eISSN：1348-0715, ORCID：50286557 - Crystalline-Si heterojunction with organic thin-layer (HOT) solar cell module using poly (3, 4-ethylenedioxythiophene): poly (styrene sulfonate)(PEDOT: PSS)
Kasahara, Koji; Hossain, Jaker; Harada, Daisuke; Ichikawa, Koki; Ishikawa, Ryo; Shirai, Hajime
Solar Energy Materials and Solar Cells, Volume：181, First page：60, Last page：70, Jul. 2018
North-Holland, Scientific journal
DOI：https://doi.org/10.1016/j.solmat.2017.10.016
DOI ID：10.1016/j.solmat.2017.10.016, ISSN：0927-0248, ORCID：50286555 - Nb-doped amorphous titanium oxide compact layer for formamidinium-based high efficiency perovskite solar cells by low-temperature fabrication
Youhei Numata; Ryo Ishikawa; Yoshitaka Sanehira; Atsushi Kogo; Hajime Shirai; Tsutomu Miyasaka
JOURNAL OF MATERIALS CHEMISTRY A, Volume：6, Number：20, First page：9583, Last page：9591, May 2018
Low-temperature processed perovskite solar cells (PSCs) were prepared using an amorphous niobium-doped titanium oxide (Nb/TiOx) film as a compact layer (CL) combined with a brookite TiO2 mesoporous layer. Nb concentration of 4% in amorphous TiOx CL was found to improve the photocurrent-voltage performances of formamidinium (FA) and methylammonium (MA)-mixed perovskite, (FAPbI(3))(0.85)(MAPbBr(3))(0.15), and FA(0.85)Cs(0.15)PbI(3) perovskite solar cells, which were fabricated on 100 degrees C and 130 degrees C-annealed TiOx CLs; these solar cells exhibited conversion efficiencies up to 19.1% and 19.8%, respectively. The Nb/TiOx-based FA(0.85)Cs(0.15)PbI(3) perovskite cell obtained entirely by a low temperature process (130 degrees C or less) exhibited high stability against light soaking without encapsulation of the device.
ROYAL SOC CHEMISTRY, English, Scientific journal
DOI：https://doi.org/10.1039/c8ta02540a
DOI ID：10.1039/c8ta02540a, ISSN：2050-7488, eISSN：2050-7496, ORCID：50286559, Web of Science ID：WOS:000433427300028 - Optical anisotropy and compositional ratio of conductive polymer PEDOT: PSS and their effect on photovoltaic performance of crystalline silicon/organic heterojunction solar cells
Hajime Shirai; Qiming Liu; Tatsuya Ohki; Ryo Ishikawa; Keiji Ueno
Advances in Silicon Solar Cells, First page：137, Last page：159, Jan. 2018, [Reviewed]
We demonstrate the optical anisotropy of a transparent conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and its effect on the photovoltaic performance of n-type crystalline silicon (n-Si)/ PEDOT:PSS heterojunction solar cells. The depth profile of PEDOT/PSS compositional ratio and optical anisotropy depends on the type of polar solvent and/or external DC bias supplied to n-Si substrate during film deposition by spin coating (SC) and chemical mist deposition (CMD). N-Si/PEDOT:PSS heterojunction solar cells with higher PEDOT/PSS compositional ratio near the film surface exhibited better power conversion efficiency η of 12.5% (@2 × 2 cm2) without any light harvesting techniques. In this chapter, the correlation among the optical anisotropy, the depth profile of PEDOT/PSS compositional ratio in conductive polymer PEDOT:PSS, and the photovoltaic performance of n-Si/PEDOT:PSS heterojunction solar cells is demonstrated.
Springer International Publishing, English, In book
DOI：https://doi.org/10.1007/978-3-319-69703-1_5
DOI ID：10.1007/978-3-319-69703-1_5, SCOPUS ID：85045552655 - Barium hydroxide hole blocking layer for front-and back-organic/crystalline Si heterojunction solar cells
Hossain, Jaker; Kasahara, Koji; Harada, Daisuke; Saiful Islam, ATM; Ishikawa, Ryo; Ueno, Keiji; Hanajiri, Tatsuro; Nakajima, Yoshikata; Fujii, Yasuhiko; Tokuda, Masahide; others
Journal of Applied Physics, Volume：122, Number：5, First page：055101, Last page：055101, Aug. 2017
AIP Publishing, Scientific journal
DOI：https://doi.org/10.1063/1.4985812
DOI ID：10.1063/1.4985812, ISSN：0021-8979, eISSN：1089-7550, ORCID：50286558 - Fabrication of {CH(NH2)2}1−xCsxPbI3 Perovskite Thin Films by Two-step Method and Its Application to Thin Film Solar Cells
Ryo Ishikawa; Keiji Ueno; Hajime Shirai
Chemistry Letters, Volume：46, Number：4, First page：612, Last page：615, Apr. 2017, [Reviewed], [Lead, Corresponding]
Oxford University Press (OUP), Scientific journal
DOI：https://doi.org/10.1246/cl.161194
DOI ID：10.1246/cl.161194, ISSN：0366-7022, eISSN：1348-0715, ORCID：50286551 - Nafion-Modified PEDOT: PSS as a Transparent Hole-Transporting Layer for High-Performance Crystalline-Si/Organic Heterojunction Solar Cells with Improved Light Soaking Stability
Hossain, Jaker; Liu, Qiming; Miura, Takuya; Kasahara, Koji; Harada, Daisuke; Ishikawa, Ryo; Ueno, Keiji; Shirai, Hajime
ACS Applied Materials & Interfaces, Volume：8, Number：46, First page：31926, Last page：31934, Nov. 2016
American Chemical Society, Scientific journal
DOI：https://doi.org/10.1021/acsami.6b10272
DOI ID：10.1021/acsami.6b10272, ISSN：1944-8244, eISSN：1944-8252, ORCID：50286544 - Role of Isopropyl Alcohol Solvent in the Synthesis of Organic–Inorganic Halide CH(NH2)2PbIxBr3–x Perovskite Thin Films by a Two-Step Method
Takanori Yamanaka; Kenta Masumori; Ryo Ishikawa; Keiji Ueno; Hajime Shirai
The Journal of Physical Chemistry C, Volume：120, Number：44, First page：25371, Last page：25377, Nov. 2016
American Chemical Society (ACS), Scientific journal
DOI：https://doi.org/10.1021/acs.jpcc.6b07527
DOI ID：10.1021/acs.jpcc.6b07527, ISSN：1932-7447, eISSN：1932-7455, SCOPUS ID：84994884896, Web of Science ID：WOS:000387737900022 - Effect of substrate bias on mist deposition of conjugated polymer on textured crystalline‐Si for efficient c‐Si/organic heterojunction solar cells
Tatsuya Ohki; Koki Ichikawa; Jaker Hossain; Yasuhiko Fujii; Tatsuro Hanajiri; Ryo Ishikawa; Keiji Ueno; Hajime Shirai
physica status solidi (a), Volume：213, Number：7, First page：1922, Last page：1925, Apr. 2016
We investigated the chemical mist deposition (CMD) of poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) on textured crystalline silicon (c‐Si) substrate for efficient c‐Si/PEDOT:PSS heterojunction solar cells. The Mie scattering observation and differential mobility analysis characterization revealed that the average size of mist particle decreased from 330 to 30–40 nm with increasing the number density and traveling velocity of mist precursor when positive dc bias of 10 kV was applied to the c‐Si substrate. The uniform deposition of PEDOT:PSS films was performed on textured c‐Si with the increased adhesion by suitably adjusting Vs and substrate temperature. A power conversion efficiency (PCE) of 11.57% was obtained with Jsc of 36.1 mA cm−2, Voc of 0.49 V, and FF of 0.66, when a positive Vs of 10 kV was applied to c‐Si substrate. Furthermore, PCE increased to 12.5% with Jsc of 35.6 mA cm−2, Voc of 0.53 V, and FF of 0.67 by adding a 20‐nm‐thick AR coating layer of molybdenum oxide MoOx (refractive index, n = 2.1) fabricated by CMD using 12 molybdo(VI) phosphoric acid n‐hydrate [H3(PMo12O40) · nH2O] as a precursor. These findings imply that CMD using negatively charged mist precursor is a possible method for the uniform deposition of PEDOT:PSS on textured c‐Si substrate for efficient c‐Si/PEDOT:PSS heterojunction solar cells.
Wiley, Scientific journal
DOI：https://doi.org/10.1002/pssa.201532951
DOI ID：10.1002/pssa.201532951, ISSN：1862-6300, eISSN：1862-6319 - Highly Efficient Solution-Processed Poly (3, 4-ethylenedio-xythiophene): Poly (styrenesulfonate)/Crystalline--Silicon Heterojunction Solar Cells with Improved Light-Induced Stability
Liu, Qiming; Ishikawa, Ryo; Funada, Shuji; Ohki, Tatsuya; Ueno, Keiji; Shirai, Hajime
Advanced Energy Materials, Volume：5, Number：17, First page：1500744, Last page：1500744, Sep. 2015
Wiley, Scientific journal
DOI：https://doi.org/10.1002/aenm.201500744
DOI ID：10.1002/aenm.201500744, ISSN：1614-6832, ORCID：50286550 - Double resonance Raman modes in monolayer and few-layer MoTe 2
Guo, Huaihong; Yang, Teng; Yamamoto, Mahito; Zhou, Lin; Ishikawa, Ryo; Ueno, Keiji; Tsukagoshi, Kazuhito; Zhang, Zhidong; Dresselhaus, Mildred S; Saito, Riichiro
Physical Review B, Volume：91, Number：20, First page：205415, Last page：205415, May 2015
American Physical Society, Scientific journal
DOI：https://doi.org/10.1103/physrevb.91.205415
DOI ID：10.1103/physrevb.91.205415, ISSN：1098-0121, eISSN：1550-235X, ORCID：50286542 - Efficient organic/polycrystalline silicon hybrid solar cells
Liu, Qiming; Ohki, Tatsuya; Liu, Dequan; Sugawara, Hiromitsu; Ishikawa, Ryo; Ueno, Keiji; Shirai, Hajime
Nano Energy, Volume：11, First page：260, Last page：266, Jan. 2015
Elsevier, Scientific journal
DOI：https://doi.org/10.1016/j.nanoen.2014.10.032
DOI ID：10.1016/j.nanoen.2014.10.032, ISSN：2211-2855, ORCID：50286556 - Improved photovoltaic response by incorporating green tea modified multiwalled carbon nanotubes in organic–inorganic hybrid solar cell
Ishwor Khatri; Qiming Liu; Ryo Ishikawa; Keiji Ueno; Hajime Shirai
Canadian Journal of Physics, Volume：92, Number：7/8, First page：849, Last page：852, Jul. 2014
In this work, multiwalled carbon nanotubes (MWCNTs) are separated and cut into short pipes using a green tea solution and embedded at interface of poly(3,4-ethylenedioxythiophene):poly(stylenesulfonate) (PEDOT:PSS)/n-Si hybrid solar cells. Devices fabricated with embedding green tea modified MWCNTs show much better performance (10.02%) than that of a device without MWCNTs (9.2%) due to better hole transportation, easy exciton splitting, and suppression of charge recombination.
Canadian Science Publishing, Scientific journal
DOI：https://doi.org/10.1139/cjp-2013-0506
DOI ID：10.1139/cjp-2013-0506, ISSN：0008-4204, eISSN：1208-6045 - Self assembled silver nanowire mesh as top electrode for organic-inorganic hybrid solar cell
Ishwor Khatri; Qiming Liu; Ryo Ishikawa; Keiji Ueno; Hajime Shirai
CANADIAN JOURNAL OF PHYSICS, Volume：92, Number：7-8, First page：867, Last page：870, Jul. 2014
We prepare transparent, selfassembled polygonal silver nanowire (AgNW) mesh by bubble template and use as top electrode for a poly (3,4ethylenedioxythiophene):poly(stylenesulfonate) (PEDOT:PSS)/n-Si hybrid solar cell. Devices were fabricated by pressing the self-assembled AgNW and ITO electrodes onto the surface of the PEDOT: PSS and device performances were compared. In identical transmittances of ITO and self-assembled AgNW (i.e., 87% transmittance at wavelength of 550 nm), the self-assembled AgNW mesh electrodes shows lower sheet resistance (8 Omega/square) with enhanced transparency in the ultraviolet and infrared regions. As a result, a device performance with an efficiency of 9.60% was obtained with the self-assembled electrode compared to 9.07% efficiency from the indium-tin oxide (ITO) electrode under 100 mW/cm(2) of AM 1.5 illumination. This study suggests the potential application of a self-assembled AgNW electrode as the transparent conducting electrode for future optoelectronic devices.
CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS, English, Scientific journal
DOI：https://doi.org/10.1139/cjp-2013-0564
DOI ID：10.1139/cjp-2013-0564, ISSN：0008-4204, eISSN：1208-6045, SCOPUS ID：84904317577, Web of Science ID：WOS:000339379500068 - Self-assembled silver nanowires as top electrode for poly(3,4-ethylenedioxythiophene): poly(stylenesulfonate)/n-silicon solar cell
Ishwor Khatri; Ayo Hoshino; Fumiya Watanabe; Qiming Liu; Ryo Ishikawa; Keiji Ueno; Hajime Shirai
THIN SOLID FILMS, Volume：558, First page：306, Last page：310, May 2014
We prepare transparent, self-assembled polygonal silver nanowire (AgNW) mesh by bubble template and transferred as top electrode in poly(3,4-ethylenedioxythiophene): poly(stylenesulfonate) (PEDOT:PSS)/n-silicon hybrid solar cell, which shows power conversion efficiency of 10.62% under 100 mW/cm(2) of AM 1.5G illuminations. The self-assembled AgNW mesh electrode exhibited a low sheet resistance (50 Omega/square) with high transmittance (87%) at a wavelength of 550 nm. In self-assembled AgNW mesh, AgNWs are well packed making continuous path for charge collection and transportation. Nevertheless, studies have also been carried out to transfer AgNWs from donor (glass or plastic) to receiver substrates (thermal release tape) and an expected reason for the transfer of AgNWs from thermal release tape to the top of PEDOT: PSS has also been proposed. (C) 2014 Elsevier B. V. All rights reserved.
ELSEVIER SCIENCE SA, English, Scientific journal
DOI：https://doi.org/10.1016/j.tsf.2014.02.073
DOI ID：10.1016/j.tsf.2014.02.073, ISSN：0040-6090, SCOPUS ID：84898785080, Web of Science ID：WOS:000334314100047 - Real-time measurement of optical anisotropy during film growth using a chemical mist deposition of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)
T. Hiate; N. Miyauchi; Q. Liu; R. Ishikawa; K. Ueno; H. Shirai
Journal of Applied Physics, Volume：115, Number：12, Mar. 2014
Real-time monitoring of optical anisotropy during growth by the chemical mist deposition of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films was carried out using spectroscopic ellipsometry. The microstructure of the grown films was found to be primarily determined by the DC bias applied to the mesh electrode. The ellipsometry results revealed that uniaxial anisotropy appeared for film thicknesses of about 5 nm and above, which corresponds to the average size of PEDOT crystallites. The extraordinary refractive index was found to be strongly correlated with the carrier mobility. Both the degree of optical anisotropy and the carrier mobility could be controlled during film growth by adjusting the DC bias.
AIP Publishing, Scientific journal
DOI：https://doi.org/10.1063/1.4869956
DOI ID：10.1063/1.4869956, ISSN：0021-8979, eISSN：1089-7550 - Improved photovoltaic performance of crystalline-Si/organic Schottky junction solar cells using ferroelectric polymers
Liu, Q; Khatri, I; Ishikawa, R; Fujimori, A; Ueno, K; Manabe, K; Nishino, H; Shirai, H
Applied Physics Letters, Volume：103, Number：16, First page：163503, Last page：163503, Oct. 2013
AIP Publishing, Scientific journal
DOI：https://doi.org/10.1063/1.4826323
DOI ID：10.1063/1.4826323, ISSN：0003-6951, eISSN：1077-3118, ORCID：50286534 - Effects of molybdenum oxide molecular doping on the chemical structure of poly (3, 4-ethylenedioxythiophene): poly (stylenesulfonate) and on carrier collection efficiency of silicon/poly (3, 4-ethylenedioxythiophene): poly (stylenesulfonate) heterojunction solar cells
Liu, Qiming; Khatri, Ishwor; Ishikawa, Ryo; Ueno, Keiji; Shirai, Hajime
Applied Physics Letters, Volume：102, Number：18, First page：183503, Last page：183503, May 2013
AIP Publishing, Scientific journal
DOI：https://doi.org/10.1063/1.4804298
DOI ID：10.1063/1.4804298, ISSN：0003-6951, eISSN：1077-3118, ORCID：50286532 - Green-tea modified multiwalled carbon nanotubes for efficient poly(3,4-ethylenedioxythiophene):poly(stylenesulfonate)/n-silicon hybrid solar cell
Ishwor Khatri; Zeguo Tang; Qiming Liu; Ryo Ishikawa; Keiji Ueno; Hajime Shirai
Applied Physics Letters, Volume：102, Number：6, Feb. 2013
Poly(3,4-ethylenedioxythiophene):poly(stylenesulfonate) (PEDOT:PSS)/n-Si hybrid solar cells were studied with and without embedding green-tea modify multiwalled carbon nanotubes (MWCNTs) at interface. Devices fabricated with embedding green-tea modified MWCNTs show much better performance than that of a device without MWCNTs with short circuit current density (Jsc), open circuit voltage (Voc), fill factor, and power conversion efficiency (η) as 30.31 mA/cm2, 0.54 V, 0.66, and 10.93%, respectively. Here, we believe that green-tea disperse MWCNTs bundles to individual and its incorporation improved built-in potential (Vb) of the device for better hole transport, easy exciton splitting, and suppression of charge recombination, thereby improving photovoltaic response.
AIP Publishing, Scientific journal
DOI：https://doi.org/10.1063/1.4792691
DOI ID：10.1063/1.4792691, ISSN：0003-6951, eISSN：1077-3118 - Efficient Organic Photovoltaic Cells Using MoO3 Hole-Transporting Layers Prepared by Simple Spin-Cast of Its Dispersion Solution in Methanol
Mayuko Kishi; Yosuke Kubo; Ryo Ishikawa; Hajime Shirai; Keiji Ueno
JAPANESE JOURNAL OF APPLIED PHYSICS, Volume：52, Number：2, Feb. 2013
MoO3 is one of the efficient hole-transporting materials for organic photovoltaic cells (OPVs). Here, a facile method of preparing the MoO3 buffer layer will be introduced. MoO3 powder was added into methanol and ultrasonication of the dispersion solution was carried out. Then the solution was centrifuged, and the supernatant was spin-cast on an indium-tin-oxide anode. On it, a photoconversion layer was prepared by spin-casting a poly(3-hexylthiophene):[6,6]-phenyl-C-61 butyric acid methyl ester (P3HT:PCBM) composite solution. The fabricated OPVs revealed an efficiency as high as 3.05%, which is better than that of P3HT:PCBM OPV with a poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) hole-transporting layer. (C) 2013 The Japan Society of Applied Physics
JAPAN SOC APPLIED PHYSICS, English, Scientific journal
DOI：https://doi.org/10.7567/JJAP.52.020202
DOI ID：10.7567/JJAP.52.020202, ISSN：0021-4922, CiNii Articles ID：40019589711, CiNii Books ID：AA12295836, ORCID：50286552, Web of Science ID：WOS:000314466800002 - Chemical mist deposition of graphene oxide and PEDOT:PSS films for crystalline Si/organic heterojunction solar cells
Ishwor Khatri; Takashi Imamura; Akira Uehara; Ryo Ishikawa; Keiji Ueno; Hajime Shirai
physica status solidi c, Volume：9, Number：10-11, First page：2134, Last page：2137, Sep. 2012
Abstract
The chemical mist deposition of graphene oxide (GO) and poly(3,4‐ethylenedioxythiophene):poly(stylenesulfonate) (PEDOT:PSS) were investigated on the crystalline silicon (c‐Si) substrate for the n‐type c‐Si/organic heterojunction solar cells. The uniform coating of GO flake with an average size of 1‐5 μm was obtained on the hydrophobic c‐Si wafer using deionized water as a solvent. The GO layer thickness could be controlled from a monolayer to a few tens of nanometres by vary‐ ing mist deposition time. The c‐Si/GO/ PEDOT:PSS heterojunction solar cells shows the efficiency improved from 8.75 to 9.27% with insertion of GO flakes a the PEDOT:PSS and c‐Si interface owing to the enhanced suppression of electron recombination and/or promotion of hole current at the anode. Furthermore, the CMD was also applied to coat conductive PEDOT:PSS films on the textured c‐Si. The η of 7.75% was obtained with a short‐circuit current of 34.22 mA/cm2, a open‐circuit voltage of 0.46 V, and a fill factor of 0.48. These findings imply that CMD is a promising method for the uniform deposition of both nanomaterials (GO) and conjugated polymer for the c‐Si/ organic heterojunction solar cells (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wiley, Scientific journal
DOI：https://doi.org/10.1002/pssc.201200132
DOI ID：10.1002/pssc.201200132, ISSN：1862-6351, eISSN：1610-1642 - Electrospray Deposition of Poly(3-hexylthiophene) Films for Crystalline Silicon/Organic Hybrid Junction Solar Cells
Tomohisa Ino; Masahiro Ono; Naoto Miyauchi; Qiming Liu; Zeguo Tang; Ryo Ishikawa; Keiji Ueno; Hajime Shirai
Japanese Journal of Applied Physics, Volume：51, Number：6R, First page：061602, Last page：061602, Jun. 2012
The electrospray deposition (ESD) of poly(3-hexylthiophene) (P3HT) films for use in crystalline silicon/organic hybrid heterojunction solar cells on a crystalline silicon (c-Si) wafer was investigated using real-time characterization by spectroscopic ellipsometry (SE). In contrast to the nonuniform deposition of products frequently obtained by spin-coating, a uniform deposition of P3HT films was achieved on flat and textured hydrophobic c-Si wafers by adjusting the deposition conditions. Similar findings were also obtained for the deposition of conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) on P3HT. The c-Si/P3HT/PEDOT:PSS heterojunction solar cells exhibited efficiencies of 4.1 and 6.3% on flat and textured c-Si wafers, respectively. These findings suggest that ESD is a promising method for the uniform deposition of P3HT and PEDOT:PSS films on flat and textured hydrophobic substrates.
IOP Publishing, Scientific journal
DOI：https://doi.org/10.1143/jjap.51.061602
DOI ID：10.1143/jjap.51.061602, ISSN：0021-4922, eISSN：1347-4065, SCOPUS ID：84863329516, Web of Science ID：WOS:000305135200010 - Efficient Crystalline Si/Poly (ethylene dioxythiophene): Poly (styrene sulfonate): Graphene Oxide Composite Heterojunction Solar Cells
Ono, Masahiro; Tang, Zeguo; Ishikawa, Ryo; Gotou, Takuya; Ueno, Keiji; Shirai, Hajime
Applied Physics Express, Volume：5, Number：3, First page：032301, Last page：032301, Feb. 2012
IOP Publishing, Scientific journal
DOI：https://doi.org/10.1143/apex.5.032301
DOI ID：10.1143/apex.5.032301, ISSN：1882-0778, eISSN：1882-0786, CiNii Articles ID：10030511172, CiNii Books ID：AA12295133, ORCID：50286539 - Electrospray-Deposited Poly (3, 4-ethylenedioxythiophene): Poly (styrene sulfonate) for Poly (3-hexylthiophene): Phenyl-C61-Butyric Acid Methyl Ester Photovoltaic Cells
Hiate, Taiga; Ino, Tomohisa; Ishikawa, Ryo; Ueno, Keiji; Shirai, Hajime
Japanese Journal of Applied Physics, Volume：51, Number：10S, 2012
IOP Publishing, Scientific journal
ORCID：50286545 - Crystalline Silicon/Graphene Oxide Hybrid Junction Solar Cells
Liu, Qiming; Wanatabe, Fumiya; Hoshino, Aya; Ishikawa, Ryo; Gotou, Takuya; Ueno, Keiji; Shirai, Hajime
Japanese Journal of Applied Physics, Volume：51, Number：10S, 2012
IOP Publishing, Scientific journal
ORCID：50286538 - Increased Organic Photovoltaic Cell Efficiency by Incorporating a Nonionic Fluorinated Surfactant Cathode Interlayer
Ishikawa, Ryo; Shirai, Hajime; Ueno, Keiji
Applied Physics Express, Volume：5, Number：12, First page：121601, Last page：121601, 2012
IOP Publishing, English, Scientific journal
ISSN：1882-0778, CiNii Articles ID：10031140406, CiNii Books ID：AA12295133, ORCID：50286536 - Highly efficient crystalline silicon/Zonyl fluorosurfactant-treated organic heterojunction solar cells
Liu, Qiming; Ono, Masahiro; Tang, Zeguo; Ishikawa, Ryo; Ueno, Keiji; Shirai, Hajime
Applied Physics Letters, Volume：100, Number：18, First page：183901, Last page：183901, 2012
AIP Publishing, Scientific journal
ORCID：50286530 - Efficient Organic Photovoltaic Cells Using Hole-Transporting MoO3 Buffer Layers Converted from Solution-Processed MoS2 Films
Shogo Kato; Ryo Ishikawa; Yosuke Kubo; Hajime Shirai; Keiji Ueno
Japanese Journal of Applied Physics, Volume：50, Number：7R, First page：071604, Last page：071604, Jul. 2011
We introduce a new method to fabricate a MoO3 hole-transporting layer for organic photovoltaic cells (OPVs). We fabricated a MoS2 film from its solution and converted it to MoO3. MoS2 has a lamellar crystal structure similar to graphite, and it can be exfoliated into monolayer MoS2 dispersible in water. Li atoms were first intercalated into van der Waals gaps of MoS2, and the compound was immersed in water to generate H2 bubbles, which broke the van der Waals bond between adjacent MoS2 layers. The produced solution of MoS2 was spin-casted on an indium tin oxide substrate, and the film was oxidized by ozone. On the converted MoO3 hole-transporting layer, an organic photoconversion layer was fabricated by spin-casting a poly(3-hexylthiophene):[6,6]-phenyl-C61 butyric acid methyl ester (P3HT:PCBM) composite solution. Fabricated OPVs revealed a power conversion efficiency as large as 3.14%, which was superior to that of P3HT/PCBM OPV with a poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) hole-transporting layer.
IOP Publishing, Scientific journal
DOI：https://doi.org/10.1143/jjap.50.071604
DOI ID：10.1143/jjap.50.071604, ISSN：0021-4922, eISSN：1347-4065, CiNii Articles ID：40018915963, CiNii Books ID：AA12295836, ORCID：50286533
- ペロブスカイト太陽電池の開発動向と特性改善
技術情報協会, [Contributor]
Dec. 2024
Japanese, Total pages：449p, Responsible for pages：120p-131p
CiNii Books：http://ci.nii.ac.jp/ncid/BD10067932
ISBN：9784867980538, CiNii Books ID：BD10067932
- 凹凸基板へのキャリア輸送層の形成とペロブスカイト太陽電池への応用
01 Apr. 2023 - 31 Mar. 2026
Grant amount(Total)：4680000, Direct funding：3600000, Indirect funding：1080000
Grant number：23K03921 - Crystalline Si/perobskite triple junction solar cells by mist deposition
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Grant-in-Aid for Scientific Research (C), 01 Apr. 2020 - 31 Mar. 2023
Saitama University
Grant amount(Total)：4290000, Direct funding：3300000, Indirect funding：990000
Grant number：20K05318 - Self-assembled passivation layer for high performance perovskite solar cells
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Early-Career Scientists, 01 Apr. 2020 - 31 Mar. 2022
Ryo Ishikawa, Saitama University
Grant amount(Total)：4290000, Direct funding：3300000, Indirect funding：990000
In perovskite solar cells, the quality of the film is essential, but the passivation of the surface and interface is necessary not only for high performance but also for high durability. Passivation by post-treatment is very useful, but its drawback is that it increases the number and time of processes.
When fluorinated polymers and fluorophosphoric acid are added to perovskite precursors, the fluorinated polymers and fluorophosphoric acid self-segregate on the surface of the perovskite thin film within a few to ten nm during film formation, as determined by depth analysis of X-ray photoelectron spectroscopy. The self-segregated fluorophosphorous materials served as a passivation layer, and a maximum photostabilized output of 20.4% was obtained without any post-treatment.
Grant number：20K14774 - Solution-processed c-Si/Perovskite 2-terminal multijuntion solar cell
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Grant-in-Aid for Scientific Research (C), 01 Apr. 2017 - 31 Mar. 2020
Shirai Hajime, Saitama University
Grant amount(Total)：4680000, Direct funding：3600000, Indirect funding：1080000
We investigated the solution-processed n-type crystalline Si(n-Si)/perovskite FACsPbI3 tandem solar cells. For the bottom n-Si/PEDOT:PSS heterojunction solar cells, we studied the solution-processed TiO2 as AR coating layer and hole-blocking layer at the cathode interface. The power conversion efficiency (PCE) increased to 15.4% by adjuting the layer thickness of TiO2. For the bottom perobskite FA0.8Cs0.2PbI3 thin-film solar cells, the PCE of 16-20% has been establihed by using TSC/DMF/CHP cosolvent using SnO2 as an electron transporting layer. We extend to the fabrication of 2-terminal monolicic tandem solar cell of n-Si/Perovksite using Ag nanowire adn obtained 14.% with a open-circuit voltage of 1.57V
Grant number：17K06341