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Journal of Energy Chemistry 2015年第6期24卷 712-716页

作者： Qing Shen Kenji Katayama taro toyoda Department of Engineering Science Faculty of Informatics and EngineeringThe University of Electro-Communications Department of Applied Chemistry Faculty of Science and EngineeringChuo University

Multiple exciton generation （MEG） dynamics in colloidal PbS quantum dots （QDs） characterized with an im- proved transient grating （TG） technique will be reported. Only one peak soon after optical absorption and a fast decay within 1 ps can be observed in the TG kinetics when the photon energy of the pump light hv is smaller than 2.7Eg （Eg： band gap between LUMO and HOMO in the QDs）, which corresponds to hot carrier cooling. When hv is greater than 2.7Eg, however, after the initial peak, the TG signal decreases first and soon increases, and then a new peak appears at about 2 to 3 ps. The initial peak and the new peak correspond to hot carriers at the higher excited state and MEG at the lowest excited state, respectively. By proposing a theoretical model, we can calculate the hot carrier cooling time constant and MEG occurrence time constant quantitatively. When MEG does not happen for hv smaller than 2.7Eg, hot carrier cools with a time con- stant of 400 fs. When MEG occurs for hv larger than 2.7Eg, hot carrier cools with a time constant as small as 200 fs, while MEG occurs with a time constant of 600 fs. The detailed hot carrier cooling and MEG occurrence dynamics characterized in this work would shed light on the further understanding of MEG mechanism of various type of semiconductor QDs.

关键词： PbS Quantum dots Multiple exciton generation Hot carrier cooling Transient grating

Ultrafast selective extraction of hot holes from cesium lead iodide perovskite films

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Journal of Energy Chemistry 2018年第4期27卷 1170-1174页

作者： Qing Shen Teresa S.Ripolles Jacky Even Yaohong Zhang Chao Ding Feng Liu Takuya Izuishi Naoki Nakazawa taro toyoda Yuhei Ogomi Shuzi Hayase Department of Engineering Science Faculty of lnformatics and EngineeringThe University of Electro-Communications1-5-1 ChofugaokaChofuTokyo 182-8585Japan Graduate School of Life Science and Systems Engineering Kyushu Institute of Technology2-4 HibikinoWakomatsuKitakyushu 808-0196Japan Fonctions Optiques pour les Technologies de l'information UMR 6082INSA35708 RennesFrance

Lead halide perovskites have some unique properties which are very promising for optoelectronic applications such as solar cells. LEDs and lasers. One important and expected application of perovskite halide semiconductors is solar cell operation including hot carriers. This advanced solar cell concept allows overcoming the Shockley-Queisser efficiency limit, thereby achieving energy conversion efficiency as high as 66% by extracting hot carriers. Understanding ultrafast photoexcited carrier dynamics and extraction in lead halide perovskites is crucial for these applications. Here, we clarify the hot carrier cooling and transfer dynamics in all-inorganic cesium lead iodide （CsPbI3） perovskite using transient absorption spectroscopy and Al2O3, poly（3-hexylthiophene-2,5-diyl）（P3HT） and TiO2 as selective contacts. We find that slow hot carrier cooling occurs on a timescale longer than 10 ps in the cases of CsPbI3/AI203 and CsPbI3/TiO2, which is attributed to hot phonon bottleneck for the high photoexcited carrier density. An efficient ultrafast hole transfer from CsPbI3 to the P3HT hole extracting layer is observed. These results suggest that hot holes can be extracted by appropriate selective contacts before energy dissipation into the halide perovskite lattice and that CsPbl3 has a potential for hot carrier solar cell applications.

关键词： CsPbI3 Perovskite Hot carrier cooling Hot hole transfer Hot phonon bottleneck

Photovoltaic Properties of CdSe Quantum Dot Sensitized Inverse Opal TiO<sub>2</sub>Solar Cells: The Effect of TiCl<sub>4</sub>Post Treatment

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Journal of Modern Physics 2017年第4期8卷 522-530页

作者： Motoki Hironaka taro toyoda Kanae Hori Yuhei Ogomi Shuzi Hayase Qing Sheng Department of Engineering Science The University of Electro-Communications Chofu Japan Graduate School of Life Science and Systems Engineering Kyushu Institute of Technology Kitakyushu Japan

Recently, semiconductor quantum dot (QD) sensitized solar cells (QDSSCs) are expected to achieve higher conversion efficiency because of the large light absorption coefficient and multiple exciton generation in QDs. The morphology of TiO2 electrode is one of the most important factors in QDSSCs. Inverse opal (IO) TiO2 electrode, which has periodic mesoporous structure, is useful for QDSSCs because of better penetration of electrolyte than conventional nanoparticulate TiO2 electrode. In addition, the ordered three dimensional structure of IO-TiO2 would be better for electron transport. We have found that open circuit voltage Voc of QDSSCs with IO-TiO2 electrodes was much higher (0.2 V) than that with nanoparticulate TiO2 electrodes. But short circuit current density Jsc was lower in the case of IO-TiO2 electrodes because of the smaller surface area of IO-TiO2. In this study, for increasing surface area of IO-TiO2, we applied TiCl4 post treatment on IO-TiO2 and investigated the effect of the post treatment on photovoltaic properties of CdSe QD sensitized IO-TiO2 solar cells. It was found that Jsc could be enhanced due to TiCl4 post treatment, but decreased again for more than one cycle treatment, which indicates excess post treatment may lead to worse penetration of electrolyte. Our results indicate that the appropriate post treatment can improve the energy conversion efficiency of the QDSSCs.

关键词： Quantum Dot Sensitized Solar Cells Inverse Opal Structure TiCl4 Post Treatment Morphology of the TiO2 Electrode

Uncovering the Detailed Mechanism behind High Efficiency Perovskite Hybrid Solar Cells by Studying Charge Separation and Recombination Dynamics

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Uncovering the Detailed Mechanism behind High Efficiency Per...

第二届新型太阳能电池学术研讨会

作者： Qing Shen Yuhei Ogomi Kenji Yoshino taro toyoda Shuzi Hayase The University of Electro-Communications CREST Japan Science and Technology Agency (JST) Kyushu Institute of Technology Miyazaki University

Organometal trihalide perovskite-based solid-state hybrid solar cells have attracted unexpected increasing interest because of the high efficiency(the record power conversion efficiency has been reported to be over 17%)and low cost for preparation.1)The high efficiency was thought to mainly originate from the strong optical absorption over a

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Effects of ligand structure on photovoltaic properties and charge transfer/recombination dynamics in PbS quantum dot heterojunction solar cells

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Effects of ligand structure on photovoltaic properties and c...

第三届新型太阳能电池学术研讨会

作者： Jin Chang Yuki Kuga taro toyoda Yuhei Ogomi Shuzi Hayase Qing Shen Nanjing Tech University The University of Electro-Communications Kyushu Institute of Technology

Apart from the geometrical morphology of nanocrystals(NCs),the surface chemistry has also shown significant effects on the physical and chemical properties of *** quantum dots(QDs) are generally capped with long-chain,electrically insulating ligands which are introduced during the synthetic *** of these molecules with shorter chain ligands has been shown necessary to decrease the inter-dot spacing and improve the electron transfer in QD thin *** a number of ligands have been applied for the surface passivation of Pb S QDs,the effects of the surface ligand on the photovoltaic properties and exciton dynamics have not been fully understood in quantum dot solar cells(QDSCs).The impact of the ligand chain length and scaffold on the photovoltaic properties and exciton dynamics in Pb S QDSCs is investigated by ultrafast transient absorption(TA) spectroscopy,temperature-dependent photoluminescence(PL) and transient photovoltage decay measurements in this *** was observed the inter-dot spacing was narrowed in Pb S QD films as the decrease of ligand chain length,resulting the enhancement of exciton coupling and electron *** the shortest ligand thioglycolic acid(TGA) leads to the smallest inter-dot spacing,it does not give the highest photocurrent in QDSCs due to its acidity and ligand-induced defects on QD *** was found that 3-mercaptopropanoic acid(MPA) gave the highest photocurrent of 15.3 m A/cm and power conversion efficiency of 2.64%.Another interesting thing is that as the capping ligand on Pb S QDs was replaced by conducting conjugated molecules,the exciton coupling was enhanced but the fabricated solar cell was *** findings in this work are useful for the deeper understanding on the effect of surface ligands on QDs and would shed light on the further improvement of QDSCs.

关键词： Quantum dots Solar cells Surface ligands Charge dynamics

Interface Engineering, Photoexcited Carrier Dynamics and Mechanism for Improving Photovoltaic Performance of Perovskite Solar Cells

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Interface Engineering, Photoexcited Carrier Dynamics and Mec...

第五届新型太阳能电池学术研讨会

作者： Qing Shen Chao Ding taro toyoda Kenji Yoshino Takashi Minemoto Shuzi Hayase The University of Electro-Communications Miyazaki University Ritsumeikan University Kyushu Institute of Technology

The interest in organometal trihalide Pb perovskite(CHNHPbI)-based solar cells has increased more and more in recent years because of the high efficiencies achieved,with a record of over 22%,and the simple low tempera...

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Effects of Interface Passivation on Photoexcited Carrier Dynamics and Photovoltaic Performance in Perovskite Solar Cells

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Effects of Interface Passivation on Photoexcited Carrier Dyn...

第四届新型太阳能电池学术研讨会

作者： Qing Shen Yuhei Ogomi taro toyoda Kenji Yoshino Takashi Minemoto Shuzi Hayase Faculty of Informatics and Engineering The University of Electro-Communications CREST Japan Science and Technology Agency(JST) Graduate School of Life Science and Systems Engineering Kyushu Institute of Technology Department of Electrical and Electronic Engineering Miyazaki University Faculty of Science and Engineering Ritsumeikan University

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A Bitcoin Address Multi-Classification Mechanism Based on Bipartite Graph-Based Maximization Consensus

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Computer Modeling in Engineering & Sciences 2024年第4期139卷 783-800页

作者： Lejun Zhang Junjie Zhang Kentaroh toyoda Yuan Liu Jing Qiu Zhihong Tian Ran Guo College of Information Engineering Yangzhou UniversityYangzhou225127China Cyberspace Institute Advanced Technology Guangzhou UniversityGuangzhou510006China Research and Development Center for E-Learning Ministry of EducationBeijing100039China Institute of High Performance Computing(IHPC) Agency for ScienceTechnology and Research(A∗STAR)Singapore138632Singapore School of Physics and Materials Science Guangzhou UniversityGuangzhou510006China

Bitcoin is widely used as the most classic electronic currency for various electronic services such as exchanges,gambling,marketplaces,and also scams such as high-yield investment *** the services operated by a Bitcoin address can help determine the risk level of that address and build an alert model *** engineering can also be used to flesh out labeled addresses and to analyze the current state of Bitcoin in a small *** this paper,we address the problem of identifying multiple classes of Bitcoin services,and for the poor classification of individual addresses that do not have significant features,we propose a Bitcoin address identification scheme based on joint multi-model prediction using the mapping relationship between addresses and *** innovation of the method is to(1)Extract as many valuable features as possible when an address is given to facilitate the multi-class service identification task.(2)Unlike the general supervised model approach,this paper proposes a joint prediction scheme for multiple learners based on address-entity mapping ***,after obtaining the overall features,the address classification and entity clustering tasks are performed separately,and the results are subjected to graph-basedmaximization *** final result ismade to baseline the individual address classification results while satisfying the constraint of having similarly behaving entities as far as *** testing and evaluating over 26,000 Bitcoin addresses,our feature extraction method captures more useful *** addition,the combined multi-learner model obtained results that exceeded the baseline classifier reaching an accuracy of 77.4%.

关键词： Bitcoin multi-service classification graph maximization consensus data security

Photovoltaics and Photoexcited Carrier Dynamics of Double-Layered CdS/CdSe Quantum Dot-Sensitized Solar Cells

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材料科学与工程（中英文A版） 2013年第9期3卷 601-608页

作者： taro toyoda Yohei Onishi Kenji Katayama Tsuguo Sawada Shuzi Hayase Qing Shen Department of Engineering Science Faculty of lnformatics and Engineering The University of Electro-Communications ChofuTokyo 182-8585 Japan CREST Japan Science and Technology Agency (JST) Kawaguchi Saitama 332-012 Japan Department of Applied Chemistry Faculty of Science and Engineering Chuo University Bunkyoku Tokyo 112-8551 Japan Japan Science and Technology Agency (JST) Kawaguchi Saitama 332-012 Japan Graduate School of Life Science and Systems Engineering Kyushu Institute of Technology Kitakyushu 808-0196 Japan

The photovoltaics of double-layered CdS/CdSe quantum dot (QD)-sensitizedsolar cells (QDSCs) were investigated. TheCdS/CdSe quantum dot was adsorbed on inverse opal (IO)-TiO 2. IO-TiO 2 electrodehas a honeycomb structure with largeinterconnected pores that lead to better infiltration despite thesmaller surface area than nanoparticulate electrode. Animprovement in the photovoltaic conversion efficiency (~ 3.8%) wasachieved compared with single-layered CdSe-QDSCs (~ 2.9%). We investigated the ultrafast photoexcited carrier dynamics (the electron and hole relaxation processes) ofCdS/CdSe-QDSCs byimproved-transient grating (TG) technique. TG technique basically depends on the refractive index changes duetophotoexcited carriers. The ultrafast carrier dynamics of CdS/CdSe- and CdSe-QDSCsshow fast (hole) and slow (electron) relaxation processes withdecay times of a fewpicoseconds and a few tens of picoseconds, respectively. The electron relaxation timewas shorter in theCdS/CdSe-QDSCs than in theCdSe-QDSCs, indicating a reduction in the numbers ofrecombination centers due to the pre-adsorbed CdS QDs layer.

关键词： CdSe量子点太阳能电池子动力学载流子光伏敏化光生 TiO2电极

Finite Abelian Groups of K3 Surfaces with Smooth Quotient

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Chinese Annals of Mathematics,Series B 2023年第1期44卷 99-162页

作者： taro HAYASHI Faculty of Agriculture Kindai UniversityNakamaticho 3327-204NaraNara 631-8505Japan

The quotient space of a K3 surface by a finite group is an Enriques surface or a rational surface if it is *** groups where the quotient space are Enriques surfaces are *** this paper,by analyzing effective divisors on smooth rational surfaces,the author will study finite groups which act faithfully on K3 surfaces such that the quotient space are *** particular,he will completely determine effective divisors on Hirzebruch surfaces such that there is a finite Abelian cover from a K3 surface to a Hirzebrunch surface such that the branch divisor is that effective ***,he will decide the Galois group and give the way to construct that Abelian cover from an effective divisor on a Hirzebruch ***,he studies the same theme for Enriques surfaces.

关键词： K3 surface Finite Abelian group Abelian cover of a smooth rational surface