博士（理学）

Manufacturing technology (mechanical, electrical/electronic, chemical engineering), Electric/electronic material engineering

Nanotechnology/Materials, Optical engineering and photonics

Informatics, Computational science

Nanotechnology/Materials, Energy chemistry

Apr. 2024 - Mar. 2028
Executive Secretary, Information Processing Society of Japan/ Quantum Software Study Group, Society

2024 - 2027
技術推進委員会 委員, 国立研究開発法人 新エネルギー・産業技術総合開発機構 (NEDO) 量子・AIハイブリッド技術のサイバー・フィジカル開発事業

2024 - 2026
採択審査委員 委員長, 国立研究開発法人 新エネルギー・産業技術総合開発機構 (NEDO) 懸賞金活用型プログラム／量子コンピュータを用いた社会問題ソリューション開発」事業に係る事業の企画運営に関する調査」の

May 2023 - Mar. 2025
技術委員, 国立研究開発法人 新エネルギー・産業技術総合開発機構 (NEDO), Government

2024 - 2025
Guest Editor, Springer Nature「AI-leveraged Quantum Computing: Bridging AI and Quantum Frontiers

2023 - 2025
採択審査委員会 委員, 国立研究開発法人 新エネルギー・産業技術総合開発機構 (NEDO) 量子・AIハイブリッド技術のサイバー・フィジカル開発事業

Jun. 2024
座長, 情報処理学会 第13回量子ソフトウェア研究会

Oct. 2019 - Mar. 2024
運営委員, 量子ソフトウェア研究会, Society

Dec. 2022
情報処理学会 第85回全国大会プログラム編成WG委員, 情報処理学会

01 Oct. 2019 - 01 Oct. 2021
Study group officer, SIG on Quantum Software, Society

Nov. 2024
Tech Day, Taiwan Institute for Information Industry
A* award, Tomah Sogabe

Nov. 2024
35th International Conference on Photovoltaic Science and Engineering (PVSEC-35)
Best Oral Presentation Award, Tomah Sogabe and Yoshitaka Okada

Nov. 2024
35th International Conference on Photovoltaic Science and Engineering (PVSEC-35)
Non-adiabatic Molecular Dynamics Calculations Combined with Time Series Machine Learning Methods for Analysis of Intermediate Level Carrier Dynamics in Er-doped GaAs
Poster Award, Yuya Makino, Yusuke Oteki, Yoshitaka Okada and Tomah Sogabe

Mar. 2024
情報処理学会 / 量子ソフトウェア研究会
オンラインシステム同定を統合したモンテカルロモデル予測制御による連続量子誤り訂正
学生発表奨励賞, 古賀 諒介;笠原 伸容;斯波 廣大;Chen Chih-Chieh;曽我部 東馬
Japan society

Elucidating the Mechanisms of the Large Stokes Shift in Isolated and Coupled PbS Quantum Dots
Hua Li; Chao Ding; Naoki Oguri; Yuuya Makino; Dong Liu; Yao Guo; Yuyao Wei; Yusheng Li; Yongge Yang; Dandan Wang; Shikai Chen; Taizo Masuda; Shuzi Hayase; Tomah Sogabe; Qing Shen
Journal of Physical Chemistry C, 128, 21, 8732-8740, 30 May 2024, Despite much effort being made, the origin of Stokes shift in colloidal quantum dot (CQD) solutions is still debatable to date, particularly in the case of QD films, which are typically used as active layers in the optoelectronic devices but have been rarely explored. Herein, we demonstrate that for QD solutions, the main origin contribution to the Stokes shift is the confined electron state (CES). In the case of QD films, in addition to the aforementioned CES, for the first time, we found that the Stokes shift is also affected by the electronic coupling strength between adjacent QDs. Overall, an improved understanding of the origin of the Stokes shift in lead sulfide (PbS) QD solutions and films can provide the key fundamental knowledge for realizing efficient optoelectronic devices.
Scientific journal

Drift–Diffusion Simulation of Intermediate Band Solar Cell: Effect of Intermediate Band Continuity Constraint
Kodai Shiba; Yoshitaka Okada; Tomah Sogabe
Journal of Nanomaterials, Hindawi Limited, 2023, 1-17, 27 Nov. 2023, Self-consistent drift–diffusion model has been widely employed to simulate the device performance of intermediate band solar cell (IBSC) under practical device configuration. However, one of the remained issues in the drift–diffusion modeled-based works is the difficulty to reach the IB carrier continuity through the self-consistent manner. In most of the previous reports the constraints were relaxed or just partially satisfied; which render the unreliable performance results and misguide the device design strategy. In this work, in order to solve this issue and to validate our results, we performed extensive simulations to fully disclose the significant effect of the IB continuity constraints by taking InAs/GaAs quantum dot-based IBSC as a model device using the semiconductor modules in COMSOL Multiphysics combined with the Fortran codes. We found that under rigorous satisfaction of IB continuity constraint, the band potential profiles for the IBSC with either doped or nondoped IB under various light illumination conditions are nearly identical to those under the dark conditions. Moreover, from the simulated current–voltage curve dependence on the light concentration ratio, we found the device performance based on drift–diffusion under rigorous IB continuity constraint showed similar tendency to the features simulated based on detailed balance principle except the much-lowered power conversion efficiency. Our work demonstrated here, serves as an accurate and reliable IBSC device design approach toward better IB material screening, efficiency improvement, optical management, and extended application in the emerging field such as the perovskite material-based IBSC.
Scientific journal

Electronic-, Optical-, and Temperature-Dependent Carrier Mobility Simulations of Perovskite-Type Liganded PbS Quantum Dot Array
Kenta Kumakura; Chih-Chieh Chen; Tomah Sogabe
Last, Advances in Condensed Matter Physics, Hindawi Limited, 2023, 1-10, 17 Aug. 2023, Recent experimental results suggest that higher mobility of perovskite-type ligand passivated PbS quantum dots (QDs) could be useful for efficient solar cell applications. However, theoretical understanding of the mechanism through first principal modeling is still lacking. In this study, electronic-, optical-, and temperature-dependent carrier mobility for perovskite ligand passivated PbS QD array is calculated by using the first-principles density functional theory (DFT) combined with the nonequilibrium Green’s function (NEGF) technique and a molecular dynamics (MD)-Landauer approach. It is found that formamidinium (FA)-liganded QDs have higher mobility and enhanced optical absorption comparing to that of Cl-liganded QDs. The difference could be understood through the intermediate band featured electronic structure.
Scientific journal

Enhanced Hot-Phonon Bottleneck Effect on Slowing Hot Carrier Cooling in Metal Halide Perovskite Quantum Dots With Alloyed A-Site.
Hua Li; Qing Wang; Yusuke Oteki; Chao Ding; Dong Liu; Yao Guo; Yusheng Li; Yuyao Wei; Dandan Wang; Yongge Yang; Taizo Masuda; Mengmeng Chen; Zheng Zhang; Tomah Sogabe; Shuzi Hayase; Yoshitaka Okada; Satoshi Iikubo; Qing Shen
Advanced materials, 35, 38, e2301834, 13 Jun. 2023, Peer-reviwed, True, A deep understanding of the effect of the A-site cation cross-exchange on the hot-carrier relaxation dynamics in perovskite quantum dots (PQDs) has profound implications on the further development of disruptive photovoltaic technologies. In this study, we investigated the hot carrier cooling kinetics of pure FAPbI3 , MAPbI3 , CsPbI3 and alloyed FA0.5 MA0.5 PbI3 , FA0.5 Cs0.5 PbI3 , and MA0.5 Cs0.5 PbI3 QDs using ultrafast transient absorption (TA) spectroscopy. The lifetimes of the initial fast cooling stage (<1 ps) of all the organic cation-containing PQDs were shorter than those of the CsPbI3 QDs, as verified by the electron-phonon coupling strength extracted from the temperature-dependent photoluminescence spectra. The lifetimes of the slow cooling stage of the alloyed PQDs were longer under illumination greater than 1 sun, which was ascribed to the introduction of co-vibrational optical phonon modes in the alloyed PQDs. This facilitated efficient acoustic phonon upconversion and enhanced the hot-phonon bottleneck effect, as demonstrated by first-principles calculations. This article is protected by copyright. All rights reserved.
Scientific journal, English

High-efficiency InAs/GaAs quantum dot intermediate band solar cell achieved through current constraint engineerin
Tomah Sogabe; Yasushi; Shoji Naoya Miyashita Daniel J. Farrell; Kodai Shiba; Hwen-Fen Hong; Yoshitaka Okada
Lead, Next Materials (Elsevier), 1, 2, 100013-1-100013-11, Apr. 2023, Peer-reviwed
Scientific journal, English

Inverse design of intermediate band solar cell via a joint drift-diffusion simulator and deep reinforcement learning scheme
Kodai Shiba; Naoya Miyashita; Okada Yoshitaka; Tomah Sogabe
Last, Japanese Jounal of Applied Physics, 2023, Peer-reviwed
Scientific journal, English

Ultrafast inverse design of quantum dot optical spectra via a joint TD-DFT learning scheme and deep reinforcement learning
Hibiki Yoshida; Katsuyoshi Sakamoto; Naoya Miyashita; Koichi Yamaguchi; Qing Shen; Yoshitaka Okada; Tomah Sogabe
Last, AIP Advances, AIP Publishing, 12, 11, 115316-115316, Dec. 2022, Peer-reviwed, Here, we report a case study on inverse design of quantum dot optical spectra using a deep reinforcement learning algorithm for the desired target optical property of semiconductor Cd _xSe _yTe _{x− y} quantum dots. Machine learning models were trained to predict the optical absorption and emission spectra by using the training dataset by time dependent density functional theory simulation. We show that the trained deep deterministic policy gradient inverse design agent can infer the molecular structure with an accuracy of less than 1 Å at a fixed computational time of milliseconds and up to 100–1000 times faster than the conventional heuristic particle swam optimization method. Most of the effective inverse design problems based on the surrogate machine learning and reinforcement learning model have been focused on the field of nano-photonics. Few attempts have been made in the field of quantum optical system in a similar manner. For the first time, our results, to our knowledge, provide concrete evidence that for computationally challenging tasks, a well-trained deep reinforcement learning agent can replace the existing quantum simulation and heuristics optimization tool, enabling fast and scalable simulations of the optical property of nanometer sized semiconductor quantum dots.
Scientific journal, English

Enhanced current generation in quantum-dot intermediate band solar cells through optimizing the position of quantum dot layers
Yusuke Oteki; Naoya Miyashita; Maxime Giteau; Kento Kitahara,Kodai; Shiba,Tomah Sogabe; Yoshitaka Okada
Optical Materials: X, Elsevier, 16, 100207-1-100207-5, Nov. 2022, Peer-reviwed
Scientific journal, English

Demonstration of in-plane miniband formation in InAs/InAsSb ultrahigh-density quantum dots by analysis of temperature dependence of photoluminescence
Tatsugi, Sho; Miyashita, Naoya; Sogabe, Tomah; Yamaguchi, Koichi
Japanese Journal of Applied Physics, IOP Publishing, 61, 10, 102009-102009, 10 Oct. 2022, Peer-reviwed, Abstract

Self-assembled InAs/InAsSb ultrahigh-density quantum dots (UHD QDs) were grown on GaAs(001) substrate by molecular beam epitaxy. The QD density was 1 × 10¹² cm⁻², and an average separation distance between adjacent QD edges was less than 3 nm. The temperature dependence of photoluminescence (PL) minimum energy of UHD QDs was measured and was divided clearly into three temperature regions: (1) fitting to upper Varshni shift at 15–80 K, (2) decreasing from upper Varshni shift from 80–180 K and (3) re-fitting to lower Varshni shift at 180–290 K. The energy difference between upper and lower Varshni curves increased with increasing QD density. This anomalous temperature dependence of PL minimum energy was demonstrated by a simulation model of miniband formation due to electronically strong coupling of adjacent QDs, including the temperature dependence of the homogeneous broadening in the QD.
Scientific journal, English

AI-Assisted Decision Making and Risk Evaluation in Uncertain Environment Using Stochastic Inverse Reinforcement Learning: American Football as A Case Study
Risa Takayanagi; Keita Takahashi; Tomah Sogabe
Last, Mathematical Problems in Engineering, Hindawi, 2022, 10 Oct. 2022, Peer-reviwed
Scientific journal, English

General Vapnik–Chervonenkis dimension bounds for quantum circuit learning
C-C. Chen; M. Sogabe; K. Shiba; K. Sakamoto; T. Sogabe
Last, Journal of Physics : Complexity, (In press), Oct. 2022, Peer-reviwed
Scientific journal, English

Model-Free Deep Recurrent Q-Network Reinforcement Learning for Quantum Circuit Architectures Design
Tomah Sogabe; Tomoaki Kimura; Chih-Chieh Chen; Kodai Shiba; Nobuhiro Kasahara; Masaru Sogabe; Katsuyoshi Sakamoto
Lead, Quantum Reports, 4, 4, 380-389, 21 Sep. 2022, Peer-reviwed
Scientific journal, English

Over 15% Efficiency PbS Quantum-Dot Solar Cells by Synergistic Effects of Three Interface Engineering : Reducing Nonradiative Recombination and Balancing Charge Carrier Extraction
C. Ding; D. Wang; D. Liu; H. Li; Y. Li; S. Hayase; T. Sogabe; T. Masuda; Y. Zhou; Y. Yao; Z. Zou; R. Wang; Q. Shen
Advanced Energy Materials, 2201676, 28 Jul. 2022, Peer-reviwed
Scientific journal, English

Quantum circuit architectures via quantum observable Markov decision process planning
T. Kimura; K. Shiba; C-C. Chen; M. Sogabe; K. Sakamoto; T. Sogabe
Last, Journal of Physics Communications, 16, 7, 14 Jul. 2022, Peer-reviwed
Scientific journal, English

Attention and masking embedded ensemble reinforcement learning for smart energy optimization and risk evaluation under uncertainties
T. Sogabe; D. Malla; C-C. Chen; K. Sakamoto
Lead, Journal of Renewable and Sustainable Energy, 14, 045501, 08 Jul. 2022, Peer-reviwed
Scientific journal, English

Hydrodynamic and Energy Transport Model Based Hot Carrier Effect in GaAs pin Solar Cell, Electronic Materials
T. Sogabe; K.Shiba; K. Sakamoto
Lead, Electronic Materials, 3, 2, 185-200, 11 May 2022, Peer-reviwed
Scientific journal, English

Quantum Dot Phase Transition Simulation with Hybrid Quantum Annealing via Metropolis-Adjusted Stochastic Gradient Langevin Dynamics
K. Shiba; R. Sugiyama; K. Yamaguchi; T. Sogabe
Last, Advances in Condensed Matter Physics, 2022, 2022, 11 Apr. 2022, Peer-reviwed
Scientific journal, English

Variational quantum circuit based reinforcement learning for POMDP and experimental imple- mentation
Tomoaki Kimura; Kodai Shiba; Chih-Chieh Chen; Masaru.Sogabe; Katsuyoshi Sakamoto; Tomah Sogabe
Mathematical Problems in Engineering, 2021, 1-11, 23 Dec. 2021, Peer-reviwed
Scientific journal, English

Quantum-inspired classification algorithm from DBSCAN-Deutsch-Jozsa support vectors and Ising prediction model
Kodai Shiba; Chih-Chieh Chen; Masaru.Sogabe; Katsuyoshi Sakamoto; Tomah Sogabe
Applied Science, 11, 22, 01 Dec. 2021, Peer-reviwed
Scientific journal, English

Experimental demonstration of energy-transfer ratchet intermediate-band solar cell
Tomah Sogabe; Chao-Yu Hung; Ryo Tamaki; Stanko Tomić; Koichi Yamaguchi; Ned Ekins-Daukes; Yoshitaka Okada
Communications Physics, Springer Science and Business Media LLC, 4, 1, Dec. 2021, A detailed balance calculation reveals an extremely high efficiency of 63.2% for intermediate-band solar cells (IBSCs) under maximum sunlight concentration. However, an actual IBSC device with an efficiency larger than the Shockley-Queisser (SQ) limit has so far not been reported. The main difficulties lie in realizing an efficient sequential two-photon absorption (STPA) which requires a sufficiently long lifetime intermediate state or intermediate band. In this article, we propose the concept of a ratchet type IBSC, utilizing a long lifetime of rare-earth ion luminescence centers in Erbium-doped GaAs. The temperature dependent differential external quantum efficiency reveals a significant STPA contribution originating from the Er³⁺ luminescence center. All the results were modeled and interpreted by integrating the ratchet effect with up-conversion along with a density functional theory (DFT) simulation. Our work demonstrates that the long lifetime energy-transfer mechanism in Er³⁺ centers contributes directly to the formation of a ratchet type IB.
Scientific journal

InAs/GaAsSb In-Plane Ultrahigh-Density Quantum Dot Lasers
M.Tanaka; K.Banda; T.Sogabe; K.Yamaguchi
Applied Physics Express, 14, 12, xx-xx, 22 Nov. 2021, Peer-reviwed
Scientific journal, English

On the expressibility and overfitting of quantum circuit learning
C-C. Chen; M.Watabe; K. Shiba; M.Sogabe; K.Sakamoto; T.Sogabe
ACM Transactions on Quantum Computing, 2, 2, 1-24, 09 Jul. 2021, Peer-reviwed
Scientific journal, English

Quantum Circuit Learning with Error Backpropagation Algorithm and Experimental Implementation
M Watabe; K Shiba; CC Chen; M Sogabe; K Sakamoto; T.Sogabe
Quantum Reports, 3, 2, 333-349, 28 May 2021, Peer-reviwed
Scientific journal, English

Low Sunlight Concentration Properties of InAs Ultrahigh-Density Quantum-Dot Solar Cells
R. Suzuki; K. Terada; K. Sakamoto; T. Sogabe; K. Yamaguchi
Jpn. J. Appl. Phys., 58, 7, 071004 1-071004 7, 24 Jun. 2019, Peer-reviwed
Scientific journal, English

Sunlight Concentration Properties of InAs/InAsSb Ultrahigh-Density Quantum -Dot Solar Cells
K. Terada; T. Togawa; F. Ozeki; K. Sakamoto; T. Sogabe; K. Yamaguchi
2019 IEEE 46th Photovoltaic Specialists Conference (PVSC), B8, 776, 2019, Peer-reviwed
International conference proceedings, English

An Approach to Renewable-Energy Dominant Grids via Distributed Electrical Energy Platform for IoT Systems
H. Ichikawa; S. Yokogawa; Y. Kawakita; K. Sawada; T. Sogabe; A. Minegishi; H. Uehara
2019 IEEE International Conference on Communications, Control, and Computing Technologies for Smart Grids (SmartGridComm), IEEE, pp. 1--6, 2019, Peer-reviwed
International conference proceedings, English

Online optimization of AGV transport systems using deep reinforcement learning
Kei Takahashi; Tomah Sogabe
NCSS: International Workshop on Networking, Computing, Systems, and Software, 9, 1, 53-57, 2019
International conference proceedings, English

Multi-agent Based Energy Balancing Management Algorithm for Smart Grid System
Dinesh Bahadur Malla; Katsuyoshi Sakamoto; Tomah Sogabe
NCSS: International Workshop on Networking, Computing, Systems, and Software, 9, 1, 58-62, 2019
International conference proceedings, English

Variational Quantum Support Vector Machine based on Deutsch-Jozsa Ranking
Koudai Shiba; Katsuyoshi Sakamoto; Tomah Sogabe
NCSS: International Workshop on Networking, Computing, Systems, and Software, 9, 1, 63-68, 2019
International conference proceedings, English

Development of Alpha Zero-based Reinforcement Learning Algorithm for Solving Partially Observable Markov Decision Process (POMDP) Problem
Tomoaki Kimura; Katsuyoshi Sakamoto; Tomah Sogabe
NCSS: International Workshop on Networking, Computing, Systems, and Software, 9, 1, 63-68, 2019
International conference proceedings, English

Quantum Circuit Learning Using Error Backpropagation
Masaya Watabe; Koudai Shiba; Katsuyoshi Sakamoto; Tomah Sogabe
NCSS: International Workshop on Networking, Computing, Systems, and Software, 9, 1, 74-82, 2019
International conference proceedings, English

Attention-masking extended deep Q network (AME-DQN) reinforcement learning algorithm for combinatory optimization of smart-grid energy
Dinesh Bahadur MALLA; Hioki TOMOYUKI; Kei TAKAHASHI; Masaru SOGABE; Katsuyoshi SAKAMOTO; Koichi YAMAGUCHI; Tomah SOGABE
Proceedings of the Annual Conference of JSAI 33rd Annual Conference, 2019(International session), 2A4E202-2A4E202, 2019
International conference proceedings, English

Multi-carrier energy hub management through deep deterministic policy gradient over continuous action space
Hioki TOMOYUKI; Tomah SOGABE; Dinesh MALLA; Kei Takahashi; Masaru Sogabe; Katsuyoshi Sakamoto; Kouichi YAMAGUCHI
Proceedings of the Annual Conference of JSAI 33rd Annual Conference, 2019 (International session), 2A4E201-2A4E201, 2019
International conference proceedings, English

Smart Grid Optimization by Deep Reinforcement Learning over Discrete and Continuous Action Space
Tomohiro Hirata; Dinesh Bahadur Malla; Katsuyoshi Sakamoto; Koichi Yamaguchi; Yoshitaka Okada; Tomah Sogabe
Bulletin of Networking, Computing, Systems, and Software, 8, 1, 19-22, Jan. 2019, Peer-reviwed
Scientific journal, English

Optical Transition and Carrier Relaxation in a Type-II InAs/GaAsSb Quantum Dot Layer
R. Sugiyama; S. Tatsugi; T. Sogabe; K. Yamaguchi
Japanese Journal of Applied Physics, 58, 1, 012004, 19 Nov. 2018, Peer-reviwed
Scientific journal, English

Growth Process and Photoluminescence Properties of In-Plane Ultrahigh-Density InAs Quantum Dots on InAsSb/GaAs(001)
Shingo Oikawa; Akinori Makaino; Tomah Sogabe; Koichi Yamaguchi
Physica Status Solidi (B) Basic Research, Wiley-VCH Verlag, 255, 4, 01 Apr. 2018, Peer-reviwed, InAs is grown on InAsSb/GaAs(001) by molecular beam epitaxy (MBE). At the initial growth of InAs, elongated small two-dimensional (2D) islands are formed on the InAsSb wetting layer (WL). As the InAs growth proceeded, 3D dots are spontaneously formed, and the underlying 2D terrace narrows. In addition, surface atoms of the 2D layer desorbed because of the strain relaxation. The 3D dot volume is larger than that estimated from the supply amount. From these results, it is found that surface atoms desorbed from the 2D layer are re-incorporated into 3D islands. The dot density reaches at 1 × 1012cm−2. The photoluminescence (PL) peak energy and full width at half maximum discontinuously changed at the critical coverage for 2D–3D growth mode transition. Particularly, the PL peak energy is almost proportional to the −0.27-th power of the average volume of 3D islands. It reveals that the carriers in these 3D islands have properties based on the 0D electron system, despite of in-plane ultrahigh density and small sizes. In addition, the relationship between PL intensity and quantum-dot density is evaluated.
Scientific journal, English

Self-Formation of InAs Quantum Dots on SiOx/Semiconductor Substrates by Molecular Beam Deposition
A. Makaino; K. Sakamoto; T. Sogabe; S. Kobayashi; K. Yamaguchi
Appl. Phys. Express, 11, 1-4, 085501, 2018, Peer-reviwed
Scientific journal, English

Hybrid Policy Gradient for Deep Reinforcement Learning
D.Malla; K.Sakamoto; K.Yamaguchi; S.Yokogawa; T.Sogabe
NCSS: International Workshop on Networking, Computing, Systems, and Software, 8, 1, 23-26, 2018
International conference proceedings, English

Development of Generic CNN Deep Learning Method Using Feature Graph
K.Takahashi; T.Numajiri; K.Sakamoto; K.Yamaguchi; T.Sogabe
2018 Sixth International Symposium on Computing and Networking Workshops (CANDARW), 235-238, 2018, Peer-reviwed
International conference proceedings, English

Photoluminescence Properties of In-Plane Ultrahigh-Density InAs Quantum Dots on GaAsSb/GaAs(001) for Solar Cell Applications
Sho Tatsuki; Ryo Sugiyama; Tomoe Kato; Tomah Sogabe; Koichi Yamaguchi
2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC), 0712-0715, 2018
International conference proceedings, English

Temperature Dependence of Luminescence Coupling Effect in InGaP/GaAs/Ge Triple Junction Solar Cells
Bernice Mae Yu Jeco; T.Sogabe; N. Ahsan; R.Tamaki; Y. Okada
Journal of Photonics for Energy, SPIE-Intl Soc Optical Eng, 8, 02, 1-6, 2018, Peer-reviwed
Scientific journal, English

High density quantum dot solar cells for concentrating photovoltaics (CPV)
Yoshitaka Okada; Yasushi Shoji; Chao-Yu Hung; Daniel J. Farrell; Tomah Sogabe
Conference Proceedings - 2017 17th IEEE International Conference on Environment and Electrical Engineering and 2017 1st IEEE Industrial and Commercial Power Systems Europe, EEEIC / I and CPS Europe 2017, Institute of Electrical and Electronics Engineers Inc., 6, 6, 1-4, 12 Jul. 2017, Peer-reviwed, For a multijunction solar cell (MJSC), the current matching in each subcell becomes the key issue to achieve high efficiency. For an intermediate band solar cell (IBSC) on the other hand, which also has a potential of achieving high efficiency, its equivalent circuit is comprised of a series/parallel circuit and thus it operates at a higher current density than a MJSC. Due to this inherent property, heat management becomes important when operated under a high concentrating condition. In this work, we propose one solution to this problem, where a wide bandgap cell is placed on top of IBSC, which serves as a current constraint cell but also leads to a higher Voc and hence cell efficiency.
International conference proceedings, English

Impact of optically nonuniform luminescence coupling effect to the limiting cell conversion efficiency in InGaP/GaAs/Ge triple junction solar cell
Bernice Mae F. Yu Jeco; Tomah Sogabe; Ryo Tamaki; Nazmul Ahsan; Yoshitaka Okada
JOURNAL OF PHOTONICS FOR ENERGY, SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 7, 3, Jul. 2017, Peer-reviwed, The impact of nonuniform spatial distribution of the luminescence coupling (LC) effect to the limiting cell conversion efficiency of multijunction solar cells (MJSCs) has been investigated. For this purpose, the laser beam induced current distribution maps of the limiting bottom cell have been acquired experimentally under varying middle-to-bottom cell LC efficiencies. The minimum and the maximum LC efficiencies demonstrated were 8.5% and 69%, respectively. To further analyze the measurement results, a quasi-two-dimensional simulation model considering the spatially nonuniform nature of the LC effect has been developed. A good agreement between the simulation and the measurement results suggests that the nonuniform LC current distribution is induced by optical phenomena such as photon escape and internal reflection. This nonuniformity then causes the absolute conversion efficiency of the limiting cell to be reduced by 1.35% at maximum LC efficiency. This reduction, when suppressed, can yield higher limiting cell conversion efficiency, which in turn may improve the overall MJSC conversion efficiency. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.
Scientific journal, English

Photoluminescence Mapping of In-Plane Ultrahigh-Density InAs Quantum Dots for Solar Cell Applications
R. Sugiyama; N. Akimoto; T. Sogabe; K. Yamaguchi
The 44th IEEE Photovoltaic Specialists Conference, pp. 2943--2945, 2017, Peer-reviwed
International conference proceedings, English

Hot Carrier Transportation Dynamics in InAs/GaAs Quantum Dot Solar Cell
T.Sogabe; K. Nii; K. Sakamoto; K. Yamaguchi; Y. Okada
44th IEEE Photovoltaic Specialists Conference(PVSC44), 1-3, 2017
International conference proceedings, English

Recent progress on quantum dot solar cells: a review
Tomah Sogabe; Qing Shen; Koichi Yamaguchi
JOURNAL OF PHOTONICS FOR ENERGY, SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 6, 4, Oct. 2016, Peer-reviwed, Semiconductor quantum dots (QDs) have a potential to increase the power conversion efficiency in photovoltaic operation because of the enhancement of photoexcitation. Recent advances in self-assembled QD solar cells (QDSCs) and colloidal QDSCs are reviewed, with a focus on understanding carrier dynamics. For intermediate-band solar cells using self-assembled QDs, suppression of a reduction of open circuit voltage presents challenges for further efficiency improvement. This reduction mechanism is discussed based on recent reports. In QD sensitized cells and QD heterojunction cells using colloidal QDs well-controlled heterointerface and surface passivation are key issues for enhancement of photovoltaic performances. The improved performances of colloidal QDSCs are presented. (C) The Authors. Published by SPIE
Scientific journal, English

Demonstration of the operation principles of intermediate band solar cells at room temperature
E. Lopez; A. Datas; I. Ramiro; P. G. Linares; E. Antolin; I. Artacho; A. Marti; A. Luque; Y. Shoji; T. Sogabe; A. Ogura; Y. Okada
SOLAR ENERGY MATERIALS AND SOLAR CELLS, ELSEVIER SCIENCE BV, 149, 15, 15-18, May 2016, Peer-reviwed, In this work we report, for the first time at room temperature, experimental results that prove, simultaneously in the same device, the two main physical principles involved in the operation of intermediate band solar cells: (1) the production of sub-bandgap photocurrent by two optical transitions through the intermediate band; (2) the generation of an output voltage which is not limited by the photon energy absorption threshold. These principles, which had always required cryogenic temperatures to be evidenced all together, are now demonstrated at room temperature on an intermediate band solar cell based on InAs quantum dots with Al0.3Ga0.7As barriers. (C) 2016 Elsevier B.V. All rights reserved.
Scientific journal, English

Growth of ErAs nanodots by molecular beam epitaxy for application to tunneling junctions in multijunction solar cells
Chao-Yu Hung; Tomah Sogabe; Naoya Miyashita; Yoshitaka Okada
JAPANESE JOURNAL OF APPLIED PHYSICS, IOP PUBLISHING LTD, 55, 2, 1229-1234, Feb. 2016, Peer-reviwed, ErAs nanodots (NDs) grown on GaAs(001) substrates by using molecular beam epitaxy (MBE) were investigated. Atomic force microscope images indicate that the size of ErAs NDs increases with deposition time and growth temperature. A calibration was performed to determine the deposition rate of ErAs in order that the size of NDs can be accurately controlled and hence optimized. Local current flow images and surface profiles around ErAs NDs were simultaneously measured to clarify the local conductivity distribution corresponding to a real space profile. Furthermore, we also fabricated and characterized an ErAs-ND-embedded GaAs tunnel junction (TJ), which resulted in a voltage drop of 30 mV for 15 A/cm(2) operation current equivalent to 1000 suns concentration, which is less than one-third of that of a conventional heavily doped tunnel junction. (C) 2016 The Japan Society of Applied Physics
Scientific journal, English

Optimization of decentralized renewable energy system by weather forecasting and deep machine learning techniques
Tomah Sogabe; Haruhisa Ichikawa; Tomah Sogabe; Katsuyoshi Sakamoto; Koichi Yamaguchi; Masaru Sogabe; Takashi Sato; Yusuke Suwa
2016 IEEE INNOVATIVE SMART GRID TECHNOLOGIES - ASIA (ISGT-ASIA), IEEE, 1014-1018, 2016, Peer-reviwed, Conventional electric energy can be easily adopted to a large scale by providing high quality electricity for wide-area transmissions. However, these energies are usually generated from exhaustible sources such as oil, natural gas, and coal, which are highly expensive in the long run and are the main causes of global warming. Meanwhile a large centralized energy system is more fragile and highly risky in countries like Japan where natural disasters occur frequently. A decentralized renewable energy system containing photovoltaic energy and wind power has been proposed as an alternative energy supply method. Within this system, the photovoltaic energy and wind power are well suited for the "local production and local consumption" with domestic energy transmission and are resilient to the unexpected disasters. The challenge of forming an optimal decentralized renewable energy system is to overcome its intrinsic disadvantages such as the instability and the limit of the power output. The research in this regard has drawn a lot of attention for the past twenty years. A decentralized renewable energy optimization problem is in principle categorized as nonlinear mixed integer programing problem(NMIP). Several challenging issues still remained in finding effective solution to NMIP through mathematical optimization. For instance, there is lack of reliable method to predict the energy generation and consumption; the weak scalability to large scale system is also existed due to the limited computing resource and the algorithm which are intrinsically not suitable for high speed computing. In this work, we report on employing the deep learning artificial intelligence techniques to predict the energy consumption and power generation together with the weather forecasting numerical simulation. The prediction and optimization are further examined by a small scale decentralized verification system (i-REMS) constructed inside the University campus. a novel optimization tool platform using Boltzmann machine algorithm for NMIP problem is also proposed for better computing scalable decentralized renewable energy system.
International conference proceedings, English

Laser Beam Induced Current (LBIC) Mapping of InGaP/GaAs/Ge Triple Junction Solar Cells with Luminescence Coupling
Bernice Mae Yu Jeco; Tomah Sogabe; Akio Ogura; Naoya Miyashita; Ryo Tamaki; Yoshitaka Okada
2016 IEEE 43RD PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC), IEEE, 1229-1234, 2016, Peer-reviwed, In this study, we introduced the laser beam induced current (LBIC) mapping method of InGaP/GaAs/Ge triple junction solar cells considering the luminescence coupling effect. Results have shown qualitative agreement between the acquired simulation and measurement data. Moreover, the current generated in the limiting subcell has been observed to be a mixture of luminescence coupling and measurement artifacts in excess of its dark current. Using the LBIC mapping method can provide spatial luminescence coupling current distribution in the subcell, which can serve as a guide on how to design multijunction solar cell that optimizes this effect.
International conference proceedings, English

In-plane coupling effect on absorption coefficients of InAs/GaAs quantum dots arrays for intermediate band solar cell
Tomic Stanko; Sogabe Tomah; Okada Yoshitaka
PROGRESS IN PHOTOVOLTAICS, 23, 5, 546-558, May 2015, Peer-reviwed
Scientific journal, English

Intermediate band solar cell with extreme broadband spectrum quantum efficiency
A. Datas; E. López; I. Ramiro; E. Antolín; A. Martí; A. Luque; R. Tamaki; Y. Shoji; T. Sogabe; Y. Okada
Physical Review Letters, 114, 157701, Apr. 2015, Peer-reviwed
Scientific journal, English

Intermediate Band Solar Cells: Recent Progress and Future Directions
Y. Okada; N. J. E-Daukes; T. Kita; R. Tamaki; M. Yoshida; A. Pusch; O. Hess; C. C. Phillips; D. J. Farrell; K. Yoshida; N. Ahsan; Y. Shoji; T. Sogabe; J. -F. Guillemoles
Appl. Phys. Rev, 2, pp. 021302-1-48, Apr. 2015, Peer-reviwed
Scientific journal, English

Voltage limitation analysis in strain-balanced InAs/GaAsN quantum dot solar cells applied to the intermediate band concept
P. G. Linares; E. López; I. Ramiro; A. Datas; E. Antolín; Y. Shoji; T. Sogabe; Y. Okada; A. Martí; A. Luque
Solar Energy Materials and Solar Cells, 132, 178-182, Jan. 2015, Peer-reviwed
Scientific journal, English

Self-consistent electrical parameter extraction from bias dependent spectral response measurements of III-V multi-junction solar cells
Sogabe Tomah; Ogura Akio; Ohba Mitsuyoshi; Okada Yoshitaka
PROGRESS IN PHOTOVOLTAICS, 23, 1, 37-48, Jan. 2015, Peer-reviwed
Scientific journal, English

Quantum dot array based intermediate band solar cell: effect of light concentration
Stanko Tomic; Tomah Sogabe; Yoshitaka Okada
2015 IEEE 42ND PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC), IEEE, 1229-1234, 2015, Peer-reviwed, Laterally coupled semiconductor quantum dot (QD) arrays emerged recently as promising structures for the next generation of high efficiency intermediate band solar cell (IBSC).We present here a method based on multi-band k.p Hamiltonian combined with periodic boundary conditions, applied to predict the electronic and optical properties of InAs/GaAs QDs based lateral QD arrays. The absorption coefficients were used to estimate the corresponding photovoltaic conversion efficiencies using the drift-diffusion transportation theory. Special attention was paid on the transition between IB to continuum states in conduction band. By comparing the experimental and theoretical results we have confirmed operation of the InAs/GaAs QD array based solar cell in the intermediate band regime.
International conference proceedings, English

Enhancement of current collection in epitaxial lift-off InAs/GaAs quantum dot thin film solar cell and concentrated photovoltaic study
Tomah Sogabe; Yasushi Shoji; Peter Mulder; John J. Schermer; Efrain Tamayo; Yoshitaka Okada
APPLIED PHYSICS LETTERS, AMER INST PHYSICS, 105, 11, 37-48, Sep. 2014, Peer-reviwed, We report the fabrication of a thin film InAs/GaAs quantum dot solar cell (QD cell) by applying epitaxial lift-off (ELO) approach to the GaAs substrate. We confirmed significant current collection enhancement (similar to 0.91 mA/cm(2)) in the ELO-InAs QD cell within the wavelength range of 700 nm-900 nm when compared to the ELO-GaAs control cell. This is almost six times of the sub-GaAs bandgap current collection (similar to 0.16 mA/cm(2)) from the wavelength range of 900 nm and beyond, we also confirmed the ELO induced resonance cavity effect was able to increase the solar cell efficiency by increasing both the short circuit current and open voltage. The electric field intensity of the resonance cavity formed in the ELO film between the Au back reflector and the GaAs front contact layer was analyzed in detail by finite-differential time-domain (FDTD) simulation. We found that the calculated current collection enhancement within the wavelength range of 700 nm-900 nm was strongly influenced by the size and shape of InAs QD. In addition, we performed concentrated light photovoltaic study and analyzed the effect of intermediate states on the open voltage under varied concentrated light intensity for the ELO-InAs QD cell. (C) 2014 AIP Publishing LLC.
Scientific journal, English

Enhancement of current collection in epitaxial lift-off InAs/GaAs quantum dot thin film solar cell and concentrated photovoltaic study
Tomah Sogabe; Yasushi Shoji; Peter Mulder; John J. Schermer; Efrain Tamayo; Yoshitaka Okada
APPLIED PHYSICS LETTERS, AMER INST PHYSICS, 105, 11, 3485-3487, Sep. 2014, Peer-reviwed, We report the fabrication of a thin film InAs/GaAs quantum dot solar cell (QD cell) by applying epitaxial lift-off (ELO) approach to the GaAs substrate. We confirmed significant current collection enhancement (similar to 0.91 mA/cm(2)) in the ELO-InAs QD cell within the wavelength range of 700 nm-900 nm when compared to the ELO-GaAs control cell. This is almost six times of the sub-GaAs bandgap current collection (similar to 0.16 mA/cm(2)) from the wavelength range of 900 nm and beyond, we also confirmed the ELO induced resonance cavity effect was able to increase the solar cell efficiency by increasing both the short circuit current and open voltage. The electric field intensity of the resonance cavity formed in the ELO film between the Au back reflector and the GaAs front contact layer was analyzed in detail by finite-differential time-domain (FDTD) simulation. We found that the calculated current collection enhancement within the wavelength range of 700 nm-900 nm was strongly influenced by the size and shape of InAs QD. In addition, we performed concentrated light photovoltaic study and analyzed the effect of intermediate states on the open voltage under varied concentrated light intensity for the ELO-InAs QD cell. (C) 2014 AIP Publishing LLC.
Scientific journal, English

Fabrication and characterization of GaAs tunnel diode and ErAs nanoparticles enhanced GaAs tunnel diode for multijunction solar cell
Tomah Sogabe; Yasushi Shoji; Mitsuyoshi Ohba; Naito Shunya; Naoya Miyashita; Chao-Yu Hung; Akio Ogura; Yoshitaka Okada
Journal of Management and Organization, Cambridge University Press, 1602, 3, 09 May 2014, Peer-reviwed, We report here the fabrication and characterization of GaAs tunnel diode (TD) and ErAs nanoparticles (Nps) enhanced GaAs TD. Four GaAs TDs with different contact area were fabricated by using MOCVD. We found extremely high peak current density of ~250A/cm2 for the TD with r=0.25mm contact area. Moreover a hysteresis loop was appeared during sweeping up and sweeping down the external voltage. A 'vector load line model' was proposed to explain the origin of the shape of the hysteresis loop and the onset of the bistability occurred at the intersect of the loadline and the current-voltage (I-V) curve of TD. Meanwhile, we have grown ErAs Nps on GaAs(100) surface by using MBE and succeeded in overgrowth of GaAs after ErAs deposition. GaAs(p+)/ErAs(Nps)/GaAs(n+) TDs were fabricated and characterized. We found the GaAs sample containing 70s deposition of ErAs showed the best TD behavior. No TD behavior was observed for the sample without addition of ErAs Nps, clearly indicating the strong tunneling enhancement effect from ErAs Nps.
Scientific journal, English

Extraction of electrical parameters in multi-junction solar cells from voltage dependent spectral response without light bias
Ogura Akio; Sogabe Tomah; Ohba Mitsuyoshi; Okada Yoshitaka
Jpn. J. Appl. Phys., Institute of Physics, 53, 6, 066601-1-066601-5, Apr. 2014, Peer-reviwed
Scientific journal, English

Intermediate-band dynamics of quantum dots solar cell in concentrator photovoltaic modules
Sogabe Tomah; Shoji Yasushi; Ohba Mitsuyoshi; Yoshida Katsuhisa; Tamaki Ryo; Hong Hwen-Fen; Wu Chih-Hung; Kuo Cherng-Tsong; Tomic Stanko; Okada Yoshitaka
SCIENTIFIC REPORTS, 4, Apr. 2014, Peer-reviwed
Scientific journal, English

Analysis of bias voltage dependent spectral response in Ga0.51In0.49P/Ga0.99In0.01As/Ge triple junction solar cell
Sogabe Tomah; Ogura Akio; Okada Yoshitaka
JOURNAL OF APPLIED PHYSICS, 115, 7, Feb. 2014, Peer-reviwed
Scientific journal, English

Fabrication and characterization of GaAs tunnel diode and ErAs nanoparticles enhanced GaAs tunnel diode for multijunction solar cell
Tomah Sogabe; Yasushi Shoji; Mitsuyoshi Ohba; Naito Shunya; Naoya Miyashita; Chao-Yu Hung; Akio Ogura; Yoshitaka Okada
Materials Research Society Symposium Proceedings, Materials Research Society, 1602, January, 1-7, 2014, Peer-reviwed, We report here the fabrication and characterization of GaAs tunnel diode (TD) and ErAs nanoparticles (Nps) enhanced GaAs TD. Four GaAs TDs with different contact area were fabricated by using MOCVD. We found extremely high peak current density of ∼250A/cm<
sup>
2<
/sup>
for the TD with r=0.25mm contact area. Moreover a hysteresis loop was appeared during sweeping up and sweeping down the external voltage. A 'vector load line model' was proposed to explain the origin of the shape of the hysteresis loop and the onset of the bistability occurred at the intersect of the loadline and the current-voltage (I-V) curve of TD. Meanwhile, we have grown ErAs Nps on GaAs(100) surface by using MBE and succeeded in overgrowth of GaAs after ErAs deposition. GaAs(p+)/ErAs(Nps)/GaAs(n+) TDs were fabricated and characterized. We found the GaAs sample containing 70s deposition of ErAs showed the best TD behavior. No TD behavior was observed for the sample without addition of ErAs Nps, clearly indicating the strong tunneling enhancement effect from ErAs Nps.
International conference proceedings, English

Enhancement of current collection in epitaxial lift-off InAs/GaAs quantum dot thin film solar cell and concentrated photovoltaic study
Tomah Sogabe; Yasushi Shoji; Peter Mulder; John Schermer; Efrain Tamayo; Yoshitaka Okada
2014 IEEE 40TH PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC), IEEE, 3485-3487, 2014, Peer-reviwed, We report the fabrication of a thin film InAs/GaAs quantum dot solar cell (QD cell) by applying epitaxial lift-off (ELO) approach to the GaAs substrate. Except the enhanced sub-GaAs bandgap current collection(similar to 0.16mA/cm(2)) from 900nm and beyond, we confirmed significant current collection enhancement (similar to 0.91mA/cm(2)) in ELO-InAs QD cell within the wavelength range of 700nm similar to 900nm. We also confirmed the ELO induced resonance cavity effect is able to increase the solar cell efficiency by increasing both the short circuit current and open voltage. The electric field intensity of the resonance cavity formed in the ELO film between the Au back reflector and the GaAs front contact layer was analyzed in detail by finite-differential time-domain (FDTD) simulation. In addition we performed concentrate photovoltaic study and analyzed the effect of intermediates states on the open voltage under varied concentrated light intensity for the ELO-InAs QD cell.
International conference proceedings, English

Intermediate Band Solar Cells
Okada Yoshitaka; Sogabe Tomah; Shoji Yasushi
Advanced Concepts in Photovoltaics, 425-454, 2014, Peer-reviwed

Theoretical analysis of GaAs/AlGaAs quantum dots in quantum wire array for intermediate band solar cell
T. Sogabe; T. Kaizu; Y. Okada; S. Tomić
Journal of Renewable Sustainable Energy, 6, 1, 011206-1-11, Jan. 2014, Peer-reviwed
Scientific journal, English

Theoretical analysis of GaAs/AlGaAs quantum dots in quantum wire array for intermediate band solar cell
Sogabe Tomah; Kaizu Toshiyuki; Okada Yoshitaka; Tomic Stanko
JOURNAL OF RENEWABLE AND SUSTAINABLE ENERGY, 6, 1, Jan. 2014, Peer-reviwed
Scientific journal, English

Local conductivity characteristics of individual ErAs island for solar cell tunnel junction application
Chao-Yu Hung; Tomah Sogabe; Naoya Miyashita; Yasushi Shoji; Shunya Naitoh; Yoshitaka Okada
2014 IEEE 40TH PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC), IEEE, 228-232, 2014, Peer-reviwed, Conductive atomic force microscopy has been used to study both the topography and electronic properties of 30nm scale ErAs islands grown by molecular beam epitaxy (MBE) on n-type GaAs substrate. A calibration method was realized to determine the growth rate of the ErAs so that we can control the size of the ErAs islands. Current flow images and surface profile around ErAs islands were simultaneously measured for local conductive distribution corresponding to real space profile, where the correlations are revealed. The conductance on ErAs islands is found to be larger than that on the GaAs buffer layer from I-V characteristics via voltage sweeping from negative to positive voltage. The I-V curve and resistance of the tunnel junction with ErAs were evaluated. It exhibits that less voltage loss can be achieved even higher than 1000 suns.
International conference proceedings, English

Analysis of GaAs/AlGaAs quantum nanodisk solar cell with intermediate band carrier transportation
Akio Ogura; Tomah Sogabe; Daniel J. Farrell; Yoshitaka Okada
2014 IEEE 40TH PHOTOVOLTAIC SPECIALIST CONFERENCE (PVSC), IEEE, 2892-2895, 2014, Peer-reviwed, We have developed an I-D drift-diffusion model for an intermediate band solar cell (IBSC) based on Scharfetter-Gummel scheme. The effect of the electron transportation in intermediate band is investigated by a rigorous solution to the electron density in IB. Due to the introduction of the electron mobility in intermediate band (IB), the electron density in IB tends to become uniform. Varying the electron mobility in IB causes the change of the potential profile and electron density in IB region. Moreover, the conversion efficiency including the electron mobility in the IB presented here decreases compared to results based on sole generation/recombination process model, which is the conventional method. However, the efficiency can be fully recovered by the light concentration, indicating the importance to enhance the electron density in lB.
International conference proceedings, English

Experimental characterization and self-consistent modeling of luminescence coupling effect in III-V multijunction solar cells
Sogabe Tomah; Ogura Akio; Hung Chao-Yu; Evstropov Valery; Mintairov Mikhail; Shvarts Maxim; Okada Yoshitaka
APPLIED PHYSICS LETTERS, 103, 26, 263907-1-263907-5, Dec. 2013, Peer-reviwed
Scientific journal, English

In-plane coupling effect in InAs/GaAs quantum dots arrays for intermediate band solar cell
Stanko Tomić; Tomah Sogabe; Yoshitaka Okada
2013 IEEE 39TH PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC), 333-336, 2013, Peer-reviwed
International conference proceedings, English

Recent progress on quantum dot intermediate band solar cells
Okada Yoshitaka; Yoshida Katsuhisa; Shoji Yasushi; Sogabe Tomah
IEICE Electronics Express, 一般社団法人 電子情報通信学会, 10, 17, 20132007-20132007, 2013, Peer-reviwed, In order to surpass the thermodynamic Shockley-Queisser limit of energy conversion efficiency of single-junction solar cells, advanced concepts using multi-junction tandem structure and quantum nanostructure are presently under intense research. Recent developments and future research opportunities in high-efficiency photovoltaics technology based on quantum dot superlattice are reviewed.
Scientific journal, English

量子コンピュータの現状と機械学習への応用
曽我部東馬
Jul. 2022, 技術情報協会/月間研究開発リーダー, 196, 13-19, Japanese, Invited, Introduction commerce magazine

5分で分かる!?有名論文ナナメ読み
曽我部東馬
2022, 情報処理, 63, 3, Japanese, Introduction scientific journal

超スマート社会の社会品質を支えるi-パワードエネルギー・システム
横川慎二; 市川晴久; 曽我部東馬; 澤田賢治; 早瀬修二; 大川富雄
Oct. 2019, 品質, 49, 3, 28-31, Japanese, Peer-reviwed, Introduction other

超スマート社会の社会品質を支えるi-パワードエネルギー・システム
横川慎二; 市川晴久; 曽我部東馬; 澤田賢治; 早瀬修二; 大川富雄
日本品質管理学会, 2019, 品質, 49, 3, 228-231, Japanese, Introduction scientific journal, 0386-8230, 40021976970, AN00354769

深層学習・深層強化学習を応用したエネルギーシステムの最適化
曽我部東馬; 横川慎二
2018, 日本信頼性学会誌 信頼性, 42, 2, 87-93, Japanese, Introduction scientific journal

製造加工分野におけるディープラーニング技術の応用 (特集 溶接の品質向上に貢献する可視化技術・画像処理技術
曽我部東馬
2018, 画像ラボ, 31, 9, 48-53, Japanese, Introduction commerce magazine

製造加工分野におけるディープラーニング技術の応用
曽我部東馬
2018, 日本塑性加工協会誌 ぷらすとす, 1, 11, 763-768, Japanese, Peer-reviwed, Introduction scientific journal

再生可能エネルギー指向自律分散グリッドーバーチャルグリッドー
横川慎二; 市川晴久; 曽我部東馬; 澤田賢治; 川喜田佑介
Jan. 2017, 日本信頼性学会誌, 39, 8-15, Japanese, Peer-reviwed, Introduction other

Pythonによる量子機械学習入門
曽我部東馬
Scholarly book, Japanese, Single work, 科学情報出版株式会社, 22 Aug. 2024, 9784910558325

機械学習・ディープラーニングを使った"異常検知"技術と導入・実用化のポイント
曽我部東馬ら
Scholarly book, Japanese, Contributor, 第7章 ディープラーニングによる異常検知技術と外観検査への活用 第4節 表面・外観検査におけるディープラーニングの手法の応用と欠陥・寿命予測解析, 技術情報協会, 20 Dec. 2022

量子技術の基礎とＲ＆Ｄへの導入、活用方法～量子コンピュータ・量子アニーリング・量子シミュレーション・量子暗号通信など
曽我部東馬ら
Scholarly book, Japanese, Joint work, 第5章第3節機械学習・AI分野における量子コンピュータ活用の可能性, 技術情報協会, 30 Oct. 2022

Hybrid quantum-classical dynamic programming algorithm
C-C. Chen; K. Shiba; M.Sogabe; K.Sakamoto; T.Sogabe
Scholarly book, English, Joint work, Advances in Intelligent Systems and Computing: 192-199(2021), Springer,Cham,, 23 Jul. 2021

Impact of Domain Knowledge’s Quality on Inverse Reinforcement Learning
R.Sogabe; D. Bahadur Malla; M.Sogabe; K.Sakamoto; T.Sogabe
Scholarly book, English, Joint work, Advances in Intelligent Systems and Computing: 97-108 (2021), Springer, Cham,, 23 Jul. 2021

Pythonによる異常検知
曽我部東馬
Scholarly book, Japanese, Single work, オーム社, 26 Feb. 2021, 本書では、機械学習による異常検知のしくみを、誤差関数に着目して解説します。読者が新しい異常検知システムを自ら構築できるようになることを最終目標とし、機械学習アルゴリズムの基本から解説していきます。
機械学習について誤差関数を中心に理解を深めることによって「外れ値とはなにか」「閾値はどのように設定すればよいか」といった異常検知における基本が自然と理解できます。そういった基礎から入りつつ、時系列データを分析する際の手法と注意点（第3章）や、深層学習を用いた応用例（第4章）といった内容まで踏み込み、最終的には自ら異常検知システムを構築できるよう導きます。
機械学習の各アルゴリズムの説明や例題などには、Pythonのコードが付いています。
自分でプログラムを実行しながら学べる入門書です。

工場・製造プロセスへのＩｏＴ・ＡＩ導入と活用の仕方
曽我部東馬ら
Scholarly book, Japanese, Joint work, 技術情報協会, 30 Jun. 2020

機械学習を中心とした異常検知技術と応用提案
曽我部 東馬; 笠原 亮介ら
Scholarly book, Japanese, Joint work, 情報機構, 26 Nov. 2019

強化学習アルゴリズム入門「平均」からはじめる基礎と応用
曽我部東馬
Scholarly book, Japanese, Single work, オーム社, 24 May 2019, AlphaGoがプロ棋士を破った2016年以降、強化学習や深層強化学習はさまざまな分野から注目を集めています。しかし、専門書では難解な専門用語や数式が多用されるため、初学者にとってはハードルが高い状態が続いていました。
本書は、そのハードルの高さを解消することを目的に制作されました。平均という初歩的な数学を使うことで、「価値」「探索」「マルコフ性」といった強化学習の基本をわかりやすく解説します。
また、各アルゴリズムについては、「多腕バンディット問題」および「グリッドワールド問題」のいずれかを用いて、比較しやすい状態で解説します。そのため、各アルゴリズムの特徴や差異がわかりやすくなっています。さらに、中核的なアルゴリズムについては、PythonとMATLABの2種類のコードを、オーム社のWebサイトおよびGithubで配布します。配布コードを実行することで、「原理→数式→プログラム」という一連の流れを直感的に把握できます。

”Intermediate Band Solar Cells” | “Advanced Concepts in Photovoltaics”
Yoshitaka Okada; Tomah Sogabe; Yasushi Shoji; edited by; A. J Nozik; G. Conibeer; M. C. Beard
Scholarly book, English, Contributor, Royal Society of Chemistry, UK., 21 Jul. 2014, 9781849735902

Risk-Hedging AI-driven Optimization in Microgrid Renewable Energy Systems
Tomah Sogabe
Invited oral presentation, English, UEC-SAARC Symposium on Emerging Technologies, Invited
Dec. 2023

Control of Orientation of Reactive Sputtering Grown MoS2 Films
M.Kim; T.Sogabe; Y.Okada
English, The 2023 IEEE Electron Devices Technology and Manufacturing (IEEE EDTM 2023), Peer-reviewed
Mar. 2023

Quantum circuit architectures via quantum observable Markov decision process planning
T. Kimura; K. Shiba; C-C. Chen; M. Sogabe; K. Sakamoto; T. Sogabe
Oral presentation, Japanese, 第6回量子ソフトウェア研究発表会, オンライン, Domestic conference
07 Jul. 2022

コアシェル量子ドットにおける第一原理非平衡輸送解析と構造逆設計
吉田 響; 坂本 克好; 山口 浩一; 曽我部 東馬
Oral presentation, Japanese, 第82回 応用物理学会秋季学術講演会, Domestic conference
10 Sep. 2021

PbS量子ドットにおける第一原理非平衡グリーン関数解析およびリガンド効果
福田 渉; 坂本 克好; 山口 浩一; 曽我部 東馬
Oral presentation, Japanese, 第82回 応用物理学会秋季学術講演会, Domestic conference
10 Sep. 2021

PbS/CdS量子ドット薄膜の光励起キャリアダイナミクス
小栗 直己; 丁 超; 早瀬 修二; 曽我部 東馬; 豊田 太郎; 沈 青
Oral presentation, Japanese, 第82回 応用物理学会秋季学術講演会, Domestic conference
10 Sep. 2021

A study on the expressibility and learnability of quantum circuit learning
Chen Chih-Chieh; 渡部雅也; 斯波廣大; 曽我部完; 坂本克好; 曽我部東馬
Oral presentation, Japanese, 第３回量子ソフトウェア研究発表会, Domestic conference
01 Jul. 2021

再生エネルギーミックスにおける深層強化学習予測・最適化技術の開発
曽我部 東馬; Dinesh Malla; 坂本 克好
Oral presentation, Japanese, 第63回自動制御連合講演会, Domestic conference
21 Nov. 2020

AI予測最適化手法を用いたペロブスカイト/PbSコロイド量子ドット中間バンド太陽電池の逆設計
斯波 廣大; 坂本 克好; 山口 浩一; 沈 青; 岡田 至崇; 曽我部 東馬
Oral presentation, Japanese, 第81回応用物理学会秋季術講演会, Domestic conference
08 Sep. 2020

Q-learning for square lattice Ising model
ChihChieh Chen; 斯波 廣大; 曽我部 完; 坂本 克好; 曽我部 東馬
Oral presentation, English, 第81回応用物理学会秋季術講演会, Domestic conference
08 Sep. 2020

量子近似最適化アルゴリズム(QAOA)を用いた複数制約条件付き最適化問題への応用
斯波 廣大; Chen Chih-Chieh; 曽我部 完; 坂本 克好; 山口 浩一; 曽我部 東馬
Oral presentation, Japanese, 第34回人工知能学会全国大会, Domestic conference
09 Jun. 2020

部分観測マルコフ決定過程(POMDP)を用いた 異常前兆予測検知手法の開発
木村 友彰; Malla Dinesh; 曽我部 完; 坂本 克好; 山口 浩一; 曽我部 東馬
Oral presentation, Japanese, 第34回人工知能学会全国大会, Domestic conference
09 Jun. 2020

ベイジアン逆強化学習を用いた異常前兆予測検知手法の開発
Malla Dinesh; 木村 友彰; 曽我部 完; 坂本 克好; 山口 浩一; 曽我部 東馬
Oral presentation, Japanese, 第34回人工知能学会全国大会, Domestic conference
09 Jun. 2020

深層強化学習を用いたアメリカンフット ボールコーチング戦略の研究
高柳 里紗; Malla Dinesh; 酒井 剛; 曽我部 東馬
Oral presentation, Japanese, 第34回人工知能学会全国大会（2020.6.9-12）, Domestic conference
09 Jun. 2020

ハイブリッド量子古典的 Ulam-von Neumann線形ソルバーベースの量子動的プログラミングアルゴリズムの開発
Chen Chih-Chieh; 斯波 廣大; 曽我部 完; 坂本 克好; 曽我部 東馬
Oral presentation, Japanese, 第34回人工知能学会全国大会, Domestic conference
09 Jun. 2020

深層強化学習を用いた AGV搬送システムのオン ライン最適化
Sung Jaebok; 高橋 慧; Malla Dinesh; 坂本 克好; 山口 浩一; 曽我部 東馬
Poster presentation, Japanese, 第34回人工知能学会全国大会, Domestic conference
09 Jun. 2020

Bootstrapping Baysian Inverse Reinforcement Learning in Robotics through VR Demonstration
Sogabe Reed; 木村 友彰; Malla Dinesh; 曽我部 完; 坂本 克好; 曽我部 東馬
Oral presentation, Japanese, 第34回人工知能学会全国大会, Domestic conference
09 Jun. 2020

密度球を用いたGraph CNN深層学習手法による渋滞予測
高橋 慧; 坂本 克好; 山口 浩一; 沼尻 匠; 曽我部 完; 曽我部 東馬
Oral presentation, Japanese, 2019年度人工知能学会全国大会（第33回）新潟県新潟市（朱鷺メッセ 新潟コンベンションセンター）, Domestic conference
04 Jun. 2019

量子コンピューティングにおける最適解の全量子探索
曽我部 東馬; 斯波 廣大; 坂本 克好; 山口 浩一; Dinesh Bahadur Malla
Oral presentation, Japanese, 2019年度人工知能学会全国大会（第33回）新潟県新潟市, Domestic conference
04 Jun. 2019

汎化ゴールにおける連続動作型ロボットアームの深層強化学習手法の開発
木村 友彰; 渡部 雅也; 坂本 克好; 山口 浩一; Dinesh Bahadur Malla; 曽我部 東馬
Oral presentation, Japanese, 2019年度人工知能学会全国大会（第33回）新潟県新潟市, Domestic conference
04 Jun. 2019

アルファゼロ型強化学習アルゴリズムを用いた最適制御手法の開発
渡部 雅也; 楊 坤; Dinesh Bahadur Malla; 坂本克好; 山口浩一; 曽我部東馬
Oral presentation, Japanese, 2019年度人工知能学会全国大会（第33回）新潟県新潟市, Domestic conference
04 Jun. 2019

量子シミュレーターを用いた畳み込み型量子自己符号化器の開発
斯波 廣大; 坂本 克好; 山口 浩一; Dinesh Bahadur Malla; 曽我部 東馬
Oral presentation, Japanese, 2019年度人工知能学会全国大会（第33回）新潟県新潟市, Domestic conference
04 Jun. 2019

深層学習・深層強化学習を応用したエネルギーシステムの組み合わせ最適化と予測
曽我部東馬
Public discourse, Japanese, 日本オペレーションズ・リサーチ学会・研究部会（エネルギーミックスの諸問題とOR）第13回研究会, 公益社団法人日本オペレーションズ・リサーチ学会, Domestic conference
18 Apr. 2019

Implementing Classical-Quantum Hybrid Machine Learning Algorithms
Tomah Sogabe
Oral presentation, English, The International Workshop on Quantum Computing, Information Processing and Machine Learning (IWQCIPML) Taipei, Taiwan, Invited, International conference
2019

Opportunities and challenges for developing hybrid quantum-classical machine learning and optimization algorithms
Tomah Sogabe
Invited oral presentation, English, D2T Special Seminar, Invited, International conference
2019

面内超高密度InAs量子ドット層を導入した量子ドット太陽電池の集光特性(2)
戸川匠; 鈴木亮介; 寺田圭佑; 坂本克好; 曽我部東馬; 山口浩一
Poster presentation, Japanese, 第66回応用物理学会春季学術講演会, Domestic conference
2019

励起子型量子ゲートシミュレーター手法による量子ドット発光解析
曽我部 東馬; 斯波 廣大; 坂本; 克好; 山口 浩一
Oral presentation, Japanese, 第80回応用物理学会秋季学術講演会, Domestic conference
2019

Self-Formation of InAs Quantum Dots on Oxide/Semiconductor Substrates by Molecular Beam Deposition
K.Yamaguchi; A.Makaino; K.Sakamoto; T.Sogabe
Oral presentation, English, Compound Semiconductor Week 2018, International conference
2018

Hybrid Policy Gradient for Deep Reinforcement Learning
Praveen singh THAKUR; Masaru Sogabe; Katsuyoshi Sakamoto; Koichi Yamaguchi; Dinesh Bahadur Malla; Shinji Yokogawa; Tomah Sogabe
Poster presentation, English, 人工知能学会全国大会論文集 第 32 回全国大会 (2018), Domestic conference
2018

離散および連続的動作空間における深層強化学習を用いたスマートアネルギーシステムの最適化
曽我部東馬; 高山将太; 坂本克好; 山口浩一; 曽我部完
Poster presentation, Japanese, 人工知能学会全国大会論文集 第 32 回全国大会 (2018), Domestic conference
2018

特徴グラフを用いた汎用型 CNN 深層学習手法の開発
高橋慧; 沼尻匠; 曽我部完; 坂本克好; 山口浩一; 横川慎二; 曽我部東馬
Poster presentation, Japanese, 人工知能学会全国大会論文集 第 32 回全国大会 (2018), Domestic conference
2018

量子自己符号化器の開発
黄川田優太; 坂本克好; 山口浩一; 横川慎二; 曽我部東馬
Poster presentation, Japanese, 人工知能学会全国大会論文集 第 32 回全国大会 (2018), Domestic conference
2018

Self-formation of in-plane ultrahigh-density InAs quantum dots and their photoluminescence properties
Makaino; K.Sakamoto; T.Sogabe and K; Yamaguchi
Oral presentation, English, Compound Semiconductor Week, International conference
2017

GRID Inc: Deep learning framework for industrial and engineering optimization application
Tomah Sogabe
Public discourse, English, Stanford Silicon Valley New Japan Project, Invited, International conference
2017

GaAsSb/GaAs(001)上の 高密度 高密度 InAs量子ドット 量子ドット 層の発光特性
杉山 涼; 立木 象; 曽我部 東馬; 山口 浩一
Oral presentation, Japanese, 第78回応用物理学会秋季学術講演会, Domestic conference
2017

面内超高密度InAs量子ドット層を導入した太陽電池におけるUrbach tailの影響
鈴木 亮介; 杉山 涼; 加藤 智恵; 曽我部 東馬; 山口 浩一
Oral presentation, Japanese, 第78回応用物理学会秋季学術講演会, Domestic conference
2017

スマートエネルギーネットワークの最適化における深層強化学習の応用
黄川田 優太; 武石 将知; 曽我部 東馬
Oral presentation, Japanese, 第60回 自動制御連合講演会, Domestic conference
2017

GaAsSb/GaAs(001)上の高密度InAs量子ドット層の発光 特性
杉山 涼; 秋元 直己; 曽我部 東馬; 山口 浩一
Oral presentation, Japanese, 第64回応用物理学会春季学術講演会, Domestic conference
2017

Spatial Distribution of Temperature Dependent luminescence coupling Current in InGaP/GaAs/Ge Triple Junction Solar Cells,
Bernice Mae Yu Jeco; T. Sogabe; Y.Okada
Oral presentation, English, PVSEC-26 Singapore, International conference
24 Oct. 2016

InAsSb/GaAs(001) 上への InAs 3 次元島成長とその発光特性
及川 信吾; 馬飼野 彰宣; 曽我部 東馬; 山口 浩一
Oral presentation, Japanese, 2016年 第77回応用物理学会秋季学術講演会, Domestic conference
15 Sep. 2016

InAs/GaAs 量子ドット太陽電池におけるホットキャリア輸送 ダイナミクス
仁井 皓大; 南 裕太; 坂本 克好; 曽我部 東馬; 山口 浩一; 岡田 至崇
Poster presentation, Japanese, 2016年 第77回応用物理学会秋季学術講演会, Domestic conference
14 Sep. 2016

量子ドット中間バンド太陽電池の高効率化メカニズム
岡田 至崇; 庄司 靖; 玉置 亮; 吉田 勝尚; 曽我部 東馬
Invited oral presentation, Japanese, 2016年 第63回応用物理学会春季学術講演会, Domestic conference
19 Mar. 2016

Device simulation of thin-film intermediate-band solar cell using drift-diffusion model and FDTD method (oral)
Ogura; M. Mori; K.Yoshida; T. Sogabe; Y. Okada
Oral presentation, English, SPIE Photonics West OPTO 2016, International conference
Feb. 2016

Photoluminescence and Photovoltaic Properties of Ultrahigh Density InAs Quantum Dots on InAsSb/GaAs(001)
K. Nii; Y. Minami; K. Sakamoto; T. Sogabe; K. Yamaguchi
Oral presentation, English, The 26th Photovotaic Sicnece and Engineering Conference (PVSEC-26), International conference
2016

Epitaxial lift off (ELO) thin film InAs/GaAs quantum dot solar cell: current status and strategies toward 30% efficiency
Tomah Sogabe
Oral presentation, English, EMN Prague Meeting, Invited, International conference
2016

Investigation of Hot Carrier Transportation Dynamics in InAs/GaAs Quantum Dot Solar Cell
Tomah Sogabe
Oral presentation, English, High Efficiency Materials for Photovoltaics workshop, Invited, International conference
2016

Experimental analysis of hot state multiple exciton generation in PbSe quantum dots and its transportation modelling,
T.Sogabe; A.Ogura; Y. Okada; Q.Shen; Y.Kuga; T. Toyoda; S.Tomić; P. D. McNaughter; P. O’Brien
Oral presentation, English, 5th International Workshop on Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructures, Hsinchu, Taiwan, International conference
Sep. 2015

Light absorption via discrete states in GaAs solar cell embedded with Er complex
C-Y.Hung; T.Sogabe; R.Tamaki; N.Miyashita; Y.Okada
Oral presentation, English, 5th International Workshop on Epitaxial Growth and Fundamental Properties of Semiconductor Nanostructures, Hsinchu, Taiwan, International conference
Sep. 2015

Device Simulation of Thin Film Solar Cell Characteristics considering Fabry-Perot Cavity Effect
M. Mori; A. Ogura; T. Sogabe; Y. Okada
Oral presentation, English, International Nano-Optoelectronics Workshop 2015, Tokyo, Japan, International conference
Aug. 2015

InAs/GaAs Quantum Dot Solar Cell with 26.8% Efficiency Achieved Through Current Constraint Engineering
T. Sogabe; Y. Shoji; C-Y. Hung; D. J. Farrell; Y. Okada
Oral presentation, English, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto, International conference
Nov. 2014

Evaluation of Conversion Efficiency for Multijunction Solar Cell with Luminescent Coupling Considering Series and Shunt Resistance Effects
A. Ogura; T. Sogabe; Y. Okada
Oral presentation, English, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto, International conference
Nov. 2014

Fabrication of Hybrid ErAs:InAs Quantum Dots for Solar Cell Application
C-Y. Hung; T. Sogabe; N. Miyashita; S. Naitoh; Y. Okada
Oral presentation, English, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto, International conference
Nov. 2014

Theory of Quantum Coupling and Efficiency in QD Array Based Intermediate Band Solar Cells
S. Tomić; T. Sogabe; Y. Okada
Oral presentation, English, The 6th World Conference on Photovoltaic Energy Conversion (WCPEC-6), Kyoto, International conference
Nov. 2014

Self-consistent modeling and bias dependent spectral response measurement of luminescence coupling effect in concentrator III-V multijunction solar cells (MJSC)
T. Sogabe; A. Ogura; C-Y Hung; V. Evstropov; M.Mintairov; M. Shvarts; Y.Okada
Oral presentation, English, 10th Conference on Concentrator Photovoltaics (CPV-10), (April, 2014, Albuquerque, New Mexico,USA), International conference
Apr. 2014

Extraction of electrical parameters in triple-junction solar cell from voltage dependent spectral response without light bias
A. Ogura; T. Sogabe; C-Y. Hung; Y. Okada
Oral presentation, English, 10th Conference on Concentrator Photovoltaics (CPV-10) , Albuquerque, New Mexico,USA, International conference
Apr. 2014

GaAs/AlGaAs quantum nanodisks in quantum wire array for intermediate band solar cell
T. Sogabe; T. Kaizu; S. Tomic; Y. Okada
Oral presentation, English, The 6th International Symposium on Innovative Solar Cells,Tokyo Tech Front, International conference
20 Jan. 2014

Electronic Structure and Optical Properties of GaAs/AlGaAs Nanodisk: A Plane Wave Expanded 14-Band K・P Study
T.Sogabe
Invited oral presentation, English, 4th International Workshop on Quantum Nanostructure Solar Cells,Kobe, Japan, International conference
Dec. 2013

Operation Characteristics of InAs Quantum Dot Intermediate-Band Solar Cells
Y. Okada; Y. Shoji; R. Tamaki; T. Sogabe
Oral presentation, English, MRS Fall Meeting, , Boston,USA, International conference
Nov. 2013

Self-consistent Approach for Modeling the Luminescent Coupling in Concentrator III-V Multijunction Solar Cells
T. Sogabe; A. Ogura; C-Y. Hung; Y.Okada
Oral presentation, English, The 23rd Photovoltaic Science and Engineering Conference (PVSEC-23), Taipei,Taiwan, International conference
30 Oct. 2013

Electrical Parameters Extraction from Voltage Dependent Spectral Response in Multi-junction Solar Cells without Bias Light
A. Ogura; T. Sogabe; Y. Saito; A. Kotagiri; Y. Okada
Oral presentation, English, The 23rd Photovoltaic Science and Engineering Conference (PVSEC-23), International conference
23 Oct. 2013

Operation Characteristics of Quantum Dot Intermediate-Band Solar Cells
Y. Okada; K. Yoshida; Y.Shoji; T. Sogabe
Oral presentation, English, JSAP-MRS Joint Symposia, Invited, Kyoto, Japan, International conference
18 Sep. 2013

自己組織化3次元量子ナノ構造の作製と高効率太陽電池応用
岡田至崇; 庄司靖; 曽我部東馬
Oral presentation, Japanese, 2013年第74回応用物理学会秋季学術講演会, Domestic conference
16 Sep. 2013

Bias voltage dependent spectral response measurement and self-consistent modeling of luminescence coupling in III-V multijunction solar cells
T.Sogabe
Nominated symposium, English, High efficiency materials for photovoltaics workshop 2013,London, UK, International conference
18 Jul. 2013

Fabrication and numerical simulation of GaAs and ErAs enhanced GaAs tunnel diodes for multijunction solar cells
T. Sogabe; Y. Shoji; M. Ohba; Y. Okada
Oral presentation, English, 2013 JSAP-MRS Joint Symposia, International conference
2013

Operation Characteristics of Quantum Dot Intermediate-Band Solar Cells
Y. Okada; K. Yoshida; Y.Shoji; T. Sogabe
Invited oral presentation, English, JSAP-MRS Joint Symposia, Invited, International conference
2013

Self-consistent Fitting of Electrical Parameters for InGaAs/Ge Dual Junction Solar Cells from Bias-dependent Spectral Response
A.Ogura; T. Sogabe; M. Ohba; Y. Okada
Oral presentation, English, 9th Conference on Concentrator Photovoltaics (CPV-9), International conference
2013

First Demonstration of InAs/GaAs Quantum Dot CPV Module
T. Sogabe; Y. Shoji; M. Ohba; H-F. Hong; C-H. Wu; C-T. Kuo; Y. Okada
Oral presentation, English, 9th Conference on Concentrator Photovoltaics (CPV-9), International conference
2013

Applications of quantum dot superlattice and plasmonic nanoparticle array in high efficiency solar cells
Tomah Sogabe
Oral presentation, English, Optics & Photonics Taiwan, International Conference 2012, Invited, National Taiwan University, Taiwan, International conference
06 Dec. 2012

Modelling of Vertical and In-plane Quantum Dots Arrays for High Efficiency Solar Cells
S.Tomić; T.Sogabe; Y.Okada
Oral presentation, English, 2012 MRS Fall Meeting, Boston,USA, International conference
Nov. 2012

Applications of quantum dot superlattice and plasmonic nanoparticle array in high efficiency solar cells
Tomah Sogabe
Oral presentation, English, Optics & Photonics Taiwan, International Conference 2012, Invited, International conference
2012

K.Bhattacharjee, Y. Zhang, T. Sogabe, C. L. Gao, M. Przybylski, and J. Kirschner. LT-STS study of atomic nanowires on Cu3N/Cu(110) surface
K.Bhattacharjee; Y. Zhang; T. Sogabe; C. L. Gao; M. Przybylski; J. Kirschner
Oral presentation, English, DIPC event Passion for Knowledge, Workshop Passion for Electrons, San Sebastian, Spain, International conference
27 Sep. 2010

Thickness-dependent oscillatory magnetic anisotropy of Fe films.
J.Li; M. Przybylski; F. Yildiz; T. Sogabe; Y. Z. Wu
Oral presentation, English, International Conference on Magnetism (ICM 2009), Karlsruhe, Germany, International conference
24 Jul. 2009

LT-STS study of Fe, Cr and Au atomic nanowires on Cu3N/Cu(110) surface
K.Bhattacharjee; T. Sogabe; V. C. Zoldan; C. L. Gao; M. Przybylski; J. Kirschner
Oral presentation, English, 20th International Colloquium on Magnetic Films and Surfaces, Berlin, Germany (ICMFS 2009), International conference
20 Jul. 2009

Oscillatory magnetic anisotropy originating from quantum well states in Fe films.
J.Li; M. Przybylski; F. Yildiz; T. Sogabe; Y. Z. Wu
Oral presentation, English, 20th International Colloquium on Magnetic Films and Surfaces (ICMFS 2009) , Berlin, Germany, International conference
20 Jul. 2009

Self-assembled Co nanorods grown on Cu(110)-(2x3)N studied by MOKE and XMCD
T. Sogabe; T. Nakagawa; Y. Takagi; M. Przybylski; T. Yokoyama
Oral presentation, English, 20th International Colloquium on Magnetic Films and Surfaces (ICMFS 2009) , Berlin, Germany, International conference
20 Jul. 2009

Cu(110)-(2x3)N上のCoナノロッドの磁気的性質
曽我部 東馬; 中川剛志; 高木康多; 横山利彦
Poster presentation, Japanese, 第22回日本放射光学会年会・放射光科学合同シンポジウム東京大学本郷キャンパス, Domestic conference
10 Jan. 2009

Self-assembled Fe nanowires on a copper nitride molecular network
T. Sogabe; D. I. Bazhanov; F. Yildiz; M. Przybylski; V. S. Stepanyuk; T. Yokoyama; J. Kirschner
Oral presentation, English, 25th European Conference on Surface Science (ECOSS 25) , Liverpool, UK, International conference
27 Jul. 2008

Out-of-plane and in-plane magnetization in exchange-coupled(Rh/FeCo)/Rh(001) multilayer structure
F.Yildiz; T. Sogabe; M. Przybylski; J. Kirschner
Oral presentation, English, 25th European Conference on Surface Science (ECOSS 25) , Liverpool, UK, International conference
27 Jul. 2008

Exchange coupling in Fe/NiO bilayers grown on vicinal Ag(001) surfaces
Y.Wu; J. Li; X.-F. Jin; F. Yildiz; T. Sogabe; M. Przybylski; J. Kirschner
Oral presentation, English, Frühjahrstagung des Arbeitskreises Festkörperphysik der Deutschen Physikalischen Gesellschaft, Berlin, Germany, International conference
25 Feb. 2008

Strong perpendicular anisotropy in alloy lms grown on Pd(001), Ir(001) and Rh(001)
F.Yildiz; F. Luo; T. Sogabe; A. Winkelmann; M. Przybylski; J. Kirschner
Oral presentation, English, Frühjahrstagung des Arbeitskreises Festkörperphysik der Deutschen Physikalischen, Gesellschaft, Berlin, Germany, International conference
25 Feb. 2008

Self-assembled Fe nanowires on (2x3)N-induced Cu(110) surface.
T. Sogabe; D. I. Bazhanov; F. Yildiz; M. Przybylski; V. S. Stepanyuk; T. Yokoyama; J. Kirschner
Oral presentation, English, Frühjahrstagung des Arbeitskreises Festkörperphysik der Deutschen Physikalischen, Gesellschaft, Berlin, Germany, International conference
25 Feb. 2008

Strongly enhanced orbital moment and perpendicular magnetic anisotropy by reduced lattice symmetry of FeCo alloy film
M.Przybylski; F. Yildiz; T. Sogabe; Y. Wu; J. Li; J. Kirschner
Oral presentation, English, International Workshop on X-Ray Spectroscopy of Magnetic Solids (XRMS 2008) , Hamburg, Germany, Invited, International conference
13 Jan. 2008

Spin reorientation transition(SRT) in magnetic ultrathin Fe film on Ag(001) Effect of chemisorption
曽我部 東馬; 中川剛志; 横山利
Poster presentation, Japanese, 第9回XAFS討論会 (XAFS9), Domestic conference
2006

Spin reorientation transitions in Fe/Ag(001) induced by gas adsorption studied by XMCD and MOKE
曽我部 東馬; 中川剛志; 横山利彦
Oral presentation, Japanese, 第19回日本放射光学会年会・放射光科学合同シンポジウム, Domestic conference
2006

Electronic states and local structures of photomagnetic CuMo cyanides studied by X-ray absorption fine structure spectroscopy
曽我部 東馬; 横山利彦; 寳角敏也; 橋本和仁; 大越慎一
Poster presentation, Japanese, 第8回XAFS討論会 (XAFS8), Domestic conference
01 Aug. 2005

放射光励起STMによる表面観察
松島 毅; 奥田 太一; 江口 豊明; 小野 雅紀; 原沢 あゆみ; 浜田 雅之; 遠山 尚秀; 鴨志田 敦史; 石川 恵美子; 曽我部東馬; 脇田 高徳; 長谷川 幸雄; 木下 豊彦
Poster presentation, Japanese, 第17回日本放射光学会年会・放射光科学合同シンポジウム, Domestic conference
2004

Si表面上のGdナノ細線の光電子分光
奥田 太一; 遠山 尚秀; 脇田 高徳; 曽我部東馬; 原沢 あゆみ; 木下 豊彦
Oral presentation, Japanese, 日本物理学会第59回年次大会, Domestic conference
2004

放射光励起STMの開発と性能評価
松島 毅; 奥田 太一; 江口 豊明; 浜田 雅之; 原沢 あゆみ; 片岡 章; 曽我部東馬; 小野 雅紀; 鴨志田 敦史; 長谷川 幸雄; 木下 豊彦
Poster presentation, Japanese, 日本物理学会第59回年次大会, Domestic conference
2004

Si 表面上の Gd 一次元鎖構造の光電子分光
奥田 太一; 遠山 尚秀; 脇田 高徳; 曽我部東馬; 原沢 あゆみ; 木下 豊彦
Oral presentation, Japanese, 日本物理学会第58回年次大会, Domestic conference
2003

高効率スピン偏極電子分析器（VLEED）の開発
奥田 太一; 脇田 高徳; 原沢 あゆみ; 松島 毅; 遠山 尚秀; 曽我部東馬; 木下 豊彦
Oral presentation, Japanese, 第16回日本放射光学会年会・放射光科学合同シンポジウム, Domestic conference
2003

The Thermal Shock Behavior of Fiber Reinforced Porous Ceramic Composite Prepared by OFM
T.Sogabe; and Z; Nakagawa
Oral presentation, English, The 40th international symposium on new wave of ceramics for the 21st century, Osaka, Japan, International conference
22 Jan. 2002

ゾル―ゲル法による酸化亜鉛薄膜に対する基板からの影響
曽我部東馬; 中川善兵衛
Poster presentation, Japanese, 日本セラミックス協会東北北海道支部発表会, Domestic conference
2000

電子工学実験第二
The University of Electro-Communications

電子工学実験第二
電気通信大学

基盤理工学専攻基礎
The University of Electro-Communications

基盤理工学専攻基礎
電気通信大学

UECパスポートセミナー
The University of Electro-Communications

UECパスポートセミナー
電気通信大学

総合コミュニケーション科学
The University of Electro-Communications

総合コミュニケーション科学
電気通信大学

AIリテラシー入門
山口大学大学院技術経営研究科

AIリテラシー入門
山口大学大学院技術経営研究科

Electrical and electronic materials engineering
Saitama University

電気電子材料工学
埼玉大学

線形システム理論
The University of Electro-Communications

線形システム理論
電気通信大学

基礎電子工学
The University of Electro-Communications

基礎電気回路
The University of Electro-Communications

基礎電子工学
The University of Electro-Communications

基礎電子工学
電気通信大学

基礎電気回路
The University of Electro-Communications

基礎電気回路
電気通信大学

応用物理学会

人工知能学会

情報処理学会

小規模創電・蓄電の統合運用を可能にするインターネット型電力プラットフォーム
横川 慎二; 川喜田 佑介; 早瀬 修二; 澤田 賢治; 曽我部 東馬; 中山 舜民; 戸辺 義人
日本学術振興会, 科学研究費助成事業, 電気通信大学, 基盤研究(B), 23H01636
01 Apr. 2023 - 31 Mar. 2027

Development of see-through solar cells for building wall openings / Reverse design and development of see-through quantum dot solar cells using AI prediction optimization method
Tomah Sogabe
NEDO, Principal investigator, Funded commissioned research
2020 - Mar. 2023

個性判別のための学習制御理論の検討
澤田賢治
日産自動車(株), Coinvestigator, Domestic joint research
2022 - 2023

「エネルギー環境分野における数理モデルと人工知能融合」
東京大学、株式会社グリッド
Principal investigator, Domestic joint research
2018 - 2023

機械学習を用いた半導体搬送システムにおける目的地到着時刻の予測」
村田機械株式会社, Principal investigator, Domestic joint research
2018 - 2020

科研挑戦的研究(開拓) 「協調給電による再生可能エネルギー指向自律分 散グリッドの開発と実証」
2017 - 2020

機械学習における基礎研究
曽我部東馬
株式会社グリッド, Principal investigator, Domestic joint research
2016 - 2020

NEDOプロジェクト 超高効率・低コストⅠⅠⅠ-Ⅴ化合物太陽光 電池モジュールの研究開発(高密度量子ドット成長技術)
山口浩一
NEDO, Coinvestigator, Funded commissioned research
2018 - 2019

「下水運転操作の深層強化学習を前提としたAI技術開発 FRAMを用いたレジリエンス分析」
株式会社明電舎, Coinvestigator, Domestic joint research
2017 - 2018

カルマンフィルタを駆使した予測アルゴリズムの開発 共同研究費
岡田至崇
東京大学先端研、(株)グリッド 慶應義塾大学, Coinvestigator, Domestic joint research
2015 - 2017

気象データや各種センサーからの情報を元に人や物の動きの予測プロジェクト
岡田至崇
東京大学先端研、(株)グリッド, Coinvestigator, Domestic joint research
2015 - 2016

太陽光発電量・気象予測プロジェクト
岡田至崇
東京大学先端研、(株)グリッド, Coinvestigator, Domestic joint research
2014 - 2015

情報処理装置、情報処理方法及び情報処理プログラム
Patent right, 曽我部 東馬, 曽我部 完, 特願2017-75545(P2017-75545), Date applied: 05 Apr. 2017, 特開2018-92570 (P2018-92570A), Date announced: 14 Jun. 2018

太陽電池
Patent right, 岡田 至崇, 曽我部 東馬, 庄司 靖, 特願2014-262496(P2014-262496), Date applied: 25 Dec. 2014, The University of Tokyo, 特開2016-122752(P2016-122752A), Date announced: 07 Jul. 2016