成果報告書詳細
管理番号20130000000219
タイトル*平成24年度中間年報 新エネルギー技術研究開発 革新的太陽光発電技術研究開発(革新型太陽電池国際研究拠点整備事業)高度秩序構造を有する薄膜多接合太陽電池の研究開発(配列制御ナノ結晶シリコン、メカニカルスタック)
公開日2013/10/31
報告書年度2012 - 2012
委託先名国立大学法人東京農工大学
プロジェクト番号P07015
部署名新エネルギー部
和文要約
英文要約Title: Controlled Nanocrystalline Silicon Material/Mechanical stack (FY2008-2014) FY2012 Annual Report


1. Fabrication of nc-Si Membrane Cells
Process technology for fabricating quantum-sized nanocrystalline silicon (nc-Si) membranes has been developed by sequential wet-processing (anodization and subsequent peeling). Large-area (5cm in diameter) and thin (about 10 µm thick) nc-Si membranes have been separated from pn-junction substrates, and then the nc-Si membrane cells were fabricated by deposition of thin film electrodes onto the both sides. Mechanical stress in these membranes was successfully suppressed by introducing a super-critical drying method.
2. Band Gap Tuning
Optical absorption and photoluminescence for nc-Si membranes obtained from pn-junction substrates confirmed that the samples meet the band gap requirement for the use as a top cell in the full spectrum multi-junction solar cell. The suitability of nc-Si membranes for the photovoltaic component has also been demonstrated by measurements of photoconduction characteristics including the spectral response.
3. Photovoltaic Measurements
A significantly large open circuit voltage (0.87 V) was observed in nc-Si membrane cells under an AM1.5 illumination. The spectral response of the nc-Si cell shows a clear blue shift compared with the conventional bulk Si cells. Key issue for increasing the short-circuit current and the fill factor without affect on the open-circuit voltage is to reduce carrier trap density in the nc-Si layer.
4. Related Photonic Functions
The photon energy transfer in blue phosphorescent nc-Si was characterized for a sample doped with rare-earth elements. Theoretical analysis of the avalanche photoconduction clarified that the impact ionization rate are enhanced in nc-Si dots with atomic disorder. Hot electron effect in nc-Si is applicable to electro-deposition of thin Si films.
In summary, the intrinsic photovoltaic behavior with a large open-circuit voltage has been shown in nc-Si membrane cells. Further studies for enhancing the photovoltaic efficiency will be intensively conducted.


1. In order to decrease the connecting resistivity of transparent conductive adhesive, reduction of ITO particles was carried out. ITO particles, with sizes from 20~25-m, were joule-heated at 800oC for 5 min in vacuum to release oxygen atoms from the particles. Oxygen vacancies generate donor sites in ITO particles for producing electron carriers. Transparent conductive adhesive with the reduced ITO particles resulted in a connecting resistivity of 1.2 cm2 in the case of 20 cm2 sized samples.
2. The hydrostatic pressing method, using the high pressure gas, was used for mechanical stack process. Thick silicon substrates with a flat surface was introduced as an under pad for stacking fragile semiconductor such as GaAs or Ge. Stacking those semiconductor materials were successfully achieved under the pressure between 4.0 x105 to 6.0x105 Pa.
3. We applied transparent conductive adhesive to fabricate multi-junction solar cells with III-V semiconductor. The underlying doped GaAs substrate of the InGaP/GaAs thin film solar cells, formed with the epitaxial method, was polished and etched. They were then subsequently stacked on Ge cells, using the transparent conductive adhesive with the reduced ITO particles. Under AM1.5 light illumination with an intensity of 0.1W/cm2, the Jsc, Voc, and the power efficiency were obtained as 12.6 mA/cm2, 2.13 V, and 16 %, respectively.
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