成果報告書詳細
管理番号20120000000811
タイトル*平成23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2012/11/28
報告書年度2011 - 2011
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
和文要約和文要約等以下本編抜粋:
1. 研究開発の内容及び成果等
サブテーマ1-1 多接合太陽電池の評価解析
格子不整合太陽電池では、転位密度の低減化(105cm-2以下)が大きな課題であり、これまで様々な構造のバッファ層の提案が試みられてきた。
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-FY2012) FY2011 Annual Report
1-1. Analysis of multi-junction solar cells: Real-time structural analyses of compositionally step graded InGaAs/GaAs(001) layers were performed at SPring-8 for lattice-mismatched tandem solar cells. From asymmetric 022 reflections by in situ X-ray reciprocal space mapping, we found that the top layer is almost strained to overshooting (OS) layers, and it is independent on thicknesses of the OS layers. This implies that the strain of solar cell active layers can be controlled from compression to tensile by changing the OS layer thickness.: 1-2. Analysis of materials and cells under concentrator operation: The power losses at each resistance component of the solar cell for concentration can be analyzed using the total 3D simulator. The 2D mapping of power consumption of the electrode, top layer, middle layer, and bottom layer resistances in the cases of centered irradiance and uniform irradiance was analyzed. In the case of centered irradiance, a large amount of electrode and top layer power consumption was observed at part of the cell. On the other hand, in the case of uniform irradiance, the balance of photocurrent became good, and the total power consumption was considerably reduced. It is important to design the electrode and top layer composition, because their power consumptions were dominant components of CPV cell efficiency.: 2-1. Development of GaInNAs middle cell by CBE: The density of N-related nonradiative recombination center, E1 was investigated under various growth conditions. We found that As source flow rate plays an important role in the density of E1 and minority-carrier lifetime.: The formation mechanisms of N-H defects were investigated by using deuterated sources. We found the N-H in MMHy and -CH3 in TDMAAs and/or MMHy molecules contributed to the formation of both N-H defects at 3098 and 2952 cm-1 in GaAsN.: 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. To improve cell efficiency, the optimization of cell structure and cell fabrication techniques is necessary.: 2-2. Crystal growth simulation for III-V-N materials: We performed first-principles calculations of the growth surface of GaAsN absorbed with hydrogen (H) atoms, assuming growth by chemical beam epitaxy. Stability analysis of the reconstructed surface structure indicated that two kinds of structures could appear under H ambient. A comparison of the substitution energy of N into various As sites in these structures shows that N more easily substituted into the site on the surface, especially that bonded with H, than that in bulk. This suggests that when N atoms are incorporated into the surface, H is also incorporated with N as an impurity. This might be the origin of the point defect causing degradation of the electrical property of GaAsN.
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