成果報告書詳細
管理番号20130000000766
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) ポストシリコン超高効率太陽電池の研究開発(集光型多接合)
公開日2014/5/9
報告書年度2012 - 2012
委託先名豊田工業大学
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:R & D on Innovative Solar Cells (International Research Center for Innovative Solar Cell Program) "Research and Development of Post-silicon solar cells for ultra-high efficiencies (Concentrator Multi-Junction Solar Cells)" (FY2008-FY2014) FY2012 Annual Report

1-1. Analysis of multi-junction solar cells
Defect analysis of InGaAs thin films on GaAs(001) vicinal substrates is carried out in order to control dislocation distribution of solar cell materials. By using a MBE system with an X-ray diffractometer, we have successfully obtained the real-time evolution of both strain relaxation and lattice tilting for the InGaAs thin films. From correlation between them, dislocation distribution at the heterointerface was discussed, and a selective rule on the slip plane of dislocations related to the vicinal direction was found.
1-2. Analysis of materials and cells under concentrator operation
We measured the operating temperature of a 550X CPV module in field operation. Moreover, we developed a thermal transfer model for the CPV module and calculated the temperature in CPV module as functions of the thermal resistance and the heat transfer coefficient using a thermal transfer simulator. The model developed can be applied to the low operating temperature design of a CPV module.
2-1. Development of GaInNAs middle cell by CBE
DLTS was deployed to study the evolution, upon electron irradiation and hydrogenation of GaAsN grown by chemical beam epitaxy, of the main nitrogen-related nonradiative recombination center (E1). On one hand, the electron irradiation was found to enhance the density of E1 depending on the fluence dose. On the other hand, the hydrogenation was found to passivate completely E1. Furthermore, two new lattice defects were only observed in hydrogenated GaAsN films. As the possible origin of E1 was tentatively associated with the split interstitial formed from one N atom and one As atom in single V-site [(N-As)As], we strongly suggested that the new hole trap took place after the dissociation of E1 and the formation of N-H complex.
We fabricated single homo-junction cells consisted of the Si-doped n-type GaAsN and undoped p-type GaAsN. The highest cell efficiency of 7.2% was obtained. We characterized the cells by QSS Suns-Voc measurement. In this measurement, we can get virtually Rs-removed I-V characteristics. Relative high efficiency of 13.7% was obtained. This result indicates the main problem of our cell is high series resistance, especially contact resistance. The optimization of cell structure and cell fabrication techniques is necessary.
2-2. Crystal growth simulation for III-V-N materials
In order to understand the growth process and its difficulties, it is important to be able to model the surface reactions at the atomic scale. To do so, we perform ab initio calculations of c4x4 periodic GaAs(100) surfaces within density functional theory (DFT). In the previous works, we showed that low-H-coverage surfaces suppress the vacancy formation and H incorporation. In the present works, we examined the H-, As- and N-conditions to obtain such surfaces. It is confirmed that control of As2 pressure is important to obtain low-H-coverage surfaces under H-rich and N-rich conditions.
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