2014 Fiscal Year Research-status Report
Investigation of co-doped GaAs:NSb/AlGaAs IBSC with ideal transition energies for high efficiency Solar Cells
| Project/Area Number |
26790007
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| Research Institution | National Institute for Materials Science |
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Principal Investigator |
エルボーグ マーティン 独立行政法人物質・材料研究機構, 若手国際研究センター, ICYS研究員 (60724630)
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| Project Period (FY) |
2014-04-01 – 2017-03-31
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| Keywords | 太陽電池 / 量子構造 / MBE、エピタキシャル / GaNAs |
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| Outline of Annual Research Achievements |
I develop co-doped dilute-nitride GaAs:NSb quantum structures for the use in Intermediate Band Solar Cells (IBSCs) to achieve an IBSC structure with ideal transition energies for the first time. I employ Deep-Level Transient Spectroscopy to analyze energy levels, carrier escape, recombination and second photon absorption in the intermediate energy states to optimize the structure. By gaining a physical understanding of the key IBSC process, the two-step photocurrent generation we hope to ultimately achieve efficiencies exceeding that of a single-junction solar cell.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
- In growth experiments the Sb incorporation rates under different growth conditions (continues growth and growth interruption) have been determined.
- Optical quality of GaNAs has been improved by Sb incorporation as confirmed by photoluminescence studies. Further improvement in crystal quality is however necessary.
- Close-to-ideal transition energies for IBSC have been achieved by fabricating GaNAs/AlGaAs QW structures with 3% N and 30% Al.
- First deep-level transient spectroscopy experiments have been carried out using a model system of GaAs/AlGaAs QDs.
- Physical understanding of the two-step photocurrent generation has been advanced by analyzing the voltage dependence this process first in the same model system.
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| Strategy for Future Research Activity |
With the incorporation of Sb in GaNAs improvement in the optical quality of the material has been achieved. This improvement is however not yet sufficient. Further optimization of growth by adjusting Sb-N ratio and growth temperature will be carried out. As an alternative option, annealing the GaNAs quantum structure embedded samples in hydrogen atmosphere is considered.
Deep-level transient spectroscopy applied to a model system of GaAs/AlGaAs QD embedded solar cells has yielded the first results of DLTS peak position and activation energy. To differentiate the thermal and tunneling escape rates as well as perform measurements under different illumination conditions, the equipment will need to be modified which is in planning now.
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| Causes of Carryover |
The main expenses for equipement are planned for the second year of the research plan. Therefore the amount of transfered research buget will be used in the second year.
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| Expenditure Plan for Carryover Budget |
DLTS measurement equipment and consumables for MBE growth,
conference presentations
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