2017 Fiscal Year Research-status Report
Luminescent and electrically conductive nano-silicon for optoelectronics and photovoltaics
| Project/Area Number |
16K04898
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| Research Institution | Nagoya University |
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Principal Investigator |
Bernard Gelloz 名古屋大学, 工学研究科(国際), 特任准教授 (40343157)
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| Project Period (FY) |
2016-04-01 – 2019-03-31
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| Keywords | ナノ結晶材料 / シリコン |
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| Outline of Annual Research Achievements |
The aim of this study is to perform fundamental and applied studies on porous nano-silicon, nano-silicon oxide, plasmonic nano-metal-silicon composite layers, and powders, for the control of nano-structure shape, size and surface chemistry, luminescence (emission spectrum, lifetime, efficiency and stability) and electrical conductivity. These materials will be applied to multi-color lighting, sensing, and photovoltaics.
The knowledge acquired in the previous year has been used in the next step: the study of the photoetching of porous Si (PSi) in HF in a view to (i) understand and characterize the photoetching effect and (ii) assess its potential for size control. Two regimes were characterized, one in which the photoetch rate is limited by the supply of photo-generated holes, and another one where it is limited by the photoetching reaction. The maximum photoetch rate was derived. A model was developed to understand photoetching. This work will be presented as invited talk in Fall 2018 ECS conference.
The photo-oxidation of PSi has been attempted. Its kinetics was found very slow and probably unusable for practical purposes. The results still represent some fundamental interests and will be continued, time permitting.
In parallel, very high and stable absolute visible luminescence quantum yield was achieved using powders of Si nanocrystals oxidized under high-pressure.
A new method of chemical modification of nano-silicon surface to replace Si-H bonds by more stable Si-C bonds has been shown. It is efficient and the resulting PSi layers are stabilized.
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
The activities devoted to Electroluminescence (EL) devices based on bipolar carrier injection could not be implemented. The main reason was the difficulty in finding facilities offering good electrical semitransparent contacts in the vicinity of our laboratory. This step is crucial. We have now confirmed a laboratory which should be able to provide these contacts and we will start the study as soon as possible.
The topic of plasmonic structures for improving the luminescence characteristics of nano-silicon has also been delayed. The reason is lack of time and the need to finish the other studies under way before starting efficiently this one.
The use of anodic oxydation to tailor the sizes of the nanostructures in porous silicon was delayed because the other technique (photoetching in HF) was very interesting from the fundamental point of view and we wanted to get all the benefits from it before moving to this second technique. It will be studied soon.
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| Strategy for Future Research Activity |
The research will continue as planned.
The control of the nano-silicon size will be carried out using photoetching and selective oxidation of nano-silicon using anodic oxidation.
Electroluminescence (EL) devices based on bipolar carrier injection will be pursued. Ways to increase the porous silicon conductivity will be studied. The balance of electrons and holes injection and flow will be optimized.
The extent of stabilization of nano-silicon that can be obtained from our new method described in the summary will be studied with luminescent samples. The effect on the conductivity will also be studied. The technique will be compared to other methods of the literature.
Plasmonic structures for improving the luminescence characteristics of nano-silicon will be studied.
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