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2014 Fiscal Year Annual Research Report

シリコン系ナノ結晶表面での多重励起子の生成

Research Project

Project/Area Number 13F03716
Research InstitutionNational Institute of Advanced Industrial Science and Technology

Principal Investigator

SVRCEK Vladimir  独立行政法人産業技術総合研究所, エネルギー・環境領域 太陽光発電工学研究センター, 主任研究員 (80462828)

Co-Investigator(Kenkyū-buntansha) LOZAC'H Mickael  独立行政法人産業技術総合研究所, エネルギー・環境領域 太陽光発電研究センター, 外国人特別研究員
Project Period (FY) 2013-04-01 – 2016-03-31
Keywordsnanocrystals
Outline of Annual Research Achievements

Alloyed silicon-tin nanocrystals (SiSn-ncs) have been successfully fabricated to satisfy two challenging points for the development of future solar cell devices: a material with an energy band gap lower than the one of silicon, and a direct bandgap material that increases greatly the absorption of the solar spectrum.
SiSn-ncs were fabricated by laser ablation in liquid media technique that generates high localized plasma on the surface of amorphous SiSn target. This method synthetized SiSn-ncs alloys that was not possible using conventional techniques such as thin film deposition, high frequency plasma enhanced chemical vapor deposition, or pulsed laser deposition. The nanoparticles generated reach a quantum confinement size about 4nm with clear atomic plans observed by transmission electron microscopy. SiSn-ncs were analyzed by synchrotron radiation XRD to estimate a Si0.88Sn0.12-ncs alloys that can correspond theoretically to direct energy gap transition. Optical bandgap was estimated to be 0.81eV by absorbance measurements, which is well below the silicon bandgap. A low concentration of oxygen on the surface of SiSn-ncs was underlined by Fourier transient infrared spectra, which is of great importance for the stability over time of the devices.

Current Status of Research Progress
Current Status of Research Progress

1: Research has progressed more than it was originally planned.

Reason

The photovoltaic properties of SiSn-ncs were also analyzed using hybrid solar cell devices. Our findings underlines an improvement of the short-circuit current for devices using conjugated polymer PTB7 mixed with SiSn-ncs as active layer. This improvement is related to a better absorption at longer wavelengths due to the low energy band gap and also due to its possible direct transition. An improvement of the open-circuit voltage is also confirmed, related to the bulk heterojunction quality. It is the first report about the photovoltaic effect of SiSn-ncs alloy.

Strategy for Future Research Activity

The main future project will focus on the realization of SiSn-ncs solar cell structures as active layer with higher concentration of Sn. For this the atomic layer deposition (ALD) is a promising technique to reach higher Sn concentration and further decrease the material bandgap. Another important parameter is the strain, and especially the tensile strain, to engineer and control the indirect to direct bandgap transition, which remains challenging to demonstrate experimentally. These research plans will be also guide by rigorous analysis of the band structure to underline the conduction and valance band position related to the direct energy gap transition, which will provide key points for the physical knowledge of this alloy. Beside, in a near future, the understanding of the optimal laser condition for the synthesis of SiSn-ncs can provide information about the relation between the energy needed for the formation, the constitution and the quantum confinement size of the SiSn-ncs alloy. According to this research plan, solar cells with SiSn-ncs as active layer will be fabricated to underline the photovoltaic properties of SiSn-ncs alloy.

  • Research Products

    (7 results)

All 2015 2014

All Presentation (7 results) (of which Invited: 3 results)

  • [Presentation] Plasma technologies for engineering of the direct energy band gap of silicon at quantum confinement size2015

    • Author(s)
      Vladimir Svrcek, Mickael Lozac’h, Davide Mariotti, Koji Matsubara
    • Organizer
      ISPlasma2015/IC-PLANTS2015
    • Place of Presentation
      Nagoya University, Nagoya, Japan
    • Year and Date
      2015-03-27
    • Invited
  • [Presentation] Semiconducting silicon-tin quantum dots as environmentally friendly material for carrier multiplication solar cell at low cost2015

    • Author(s)
      Vladimir Svrcek, Mickael Lozac’h , Davide Mariotti,
    • Organizer
      The 62st JSAP Spring Meeting
    • Place of Presentation
      Tokai University, Kanagawa, Japan
    • Year and Date
      2015-03-13
  • [Presentation] Semiconducting Alloyed Silicon-Tin Nanocrystals as Up Converter Layer for Hybrid Solar Cells2015

    • Author(s)
      Mickael Lozac’h, Vladimir Svrcek, Davide Mariotti, Koji Matsubara
    • Organizer
      The 2015 Symposium for the Promotion of Applied Research Collaboration in Asia
    • Place of Presentation
      Taipei University, Taipei, Taiwan
    • Year and Date
      2015-02-10
    • Invited
  • [Presentation] Alloyed Silicon-Tin Nanocrystals with Quantum Confinement Effect applied for Hybrid Solar Cells2014

    • Author(s)
      Mickael Lozac’h, Vladimir Svrcek, Davide Mariotti, Koji Matsubara
    • Organizer
      WCPEC-6
    • Place of Presentation
      Conventional Center, Kyoto, Japan
    • Year and Date
      2014-11-26
  • [Presentation] Microplasma induced silicon quantum dots surface and energy band gap engineering.2014

    • Author(s)
      Vladimir Svrcek, Mickael Lozac’h, Somak Mitra, Davide Mariotti
    • Organizer
      International Workshop on Young Professionals in Microplasma Research
    • Place of Presentation
      Bochum University, Bochum, Germany
    • Year and Date
      2014-11-25
    • Invited
  • [Presentation] Engineering of the direct energy band gap of silicon at quantum confinement size2014

    • Author(s)
      Vladimir Svrcek, Mickael Lozac’h, Somak Mitra, Davide Mariotti and Koji Matsubara
    • Organizer
      AIST-NREL Joint Workshop on PV
    • Place of Presentation
      Fukushima AIST-FREA, Koriyama, Japan
    • Year and Date
      2014-11-21
  • [Presentation] Enhanced Conversion Efficiency of Hybrid Solar Cells by using Alloyed Silicon-TinNanocrystals via Quantum Confinement Effect2014

    • Author(s)
      Mickaël Lozac’h, Vladimir Svrcek, Davide Mariotti, and Koji Matsubara
    • Organizer
      International Conference on Solid State Devices and Materials
    • Place of Presentation
      Tsukuba Epochal, Tsukuba, Japan
    • Year and Date
      2014-09-10

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Published: 2016-06-01  

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