成果報告書詳細
管理番号20120000000793
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(ナノハイブリッド太陽電池)
公開日2012/11/28
報告書年度2011 - 2011
委託先名JX日鉱日石エネルギー株式会社
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
1.1 研究開発の内容
革新的太陽光発電技術研究開発は、地球温暖化対策として温室効果ガスの大幅削減に寄与するために、太陽光発電の性能を飛躍的に向上させることを目的とする。また、2050年に向けた長期的視野に立ち、国内の知見・技術を結集して、新材料・新規構造等を利用した革新的な太陽光発電技術を開発することで、日本の技術的優位性を超長期に渡って維持し、産業競争力強化に資することを目的とし、2050年までに「変換効率が40%超」かつ「発電コストが汎用電力料金並み(7円/kWh)」の太陽電池を実用化することを目指した研究開発の中で、変換効率40%超を実現する研究開発と、合わせて、その基礎・探索研究段階と位置づけて研究開発を実施する。
英文要約Title:New Energy Technology Development R&D for Innovative PV System Technologies Post-silicon solar cells for ultra-high efficiencies (FY2008-FY2012) FY2011 Annual Report
Quantum structured solar cells, in which quantum structures such as quantum dots (QDs) and multiple quantum wells (MQWs) are inserted in single-gap solar cells, are currently attracting wide interest due to their potential for achieving high conversion efficiency. The cells can generate photocurrent from sub-bandgap photons without voltage degradation because of the intermediate band mechanism. However, the intermediate band impact on the cell performance is still insufficient mainly due to the weak absorption coefficient associated to the quantum structures. One way of increasing this absorption is to grow more quantum layers, but this introduces strain-induced dislocations that deteriorate the device performance. Procedures for reducing the strain are in development, but this is still a challenging problem. In this study, we design and investigate the effect of metal nanostructures sustaining surface plasmons on rear surfaces of quantum structured solar cells for light trapping. The light-scattering nature of metal nanostructures can amplify the absorption by quantum structures, allowing to reduce the device thickness. The finite-difference time domain (FDTD) method was used to analyze the optical behavior of light scattered by the metal nanostructures formed on the rear surfaces of InAs/GaNAs QD solar cells. The nanostructures reflect the incident light back to the QD layers with a wide range of angles, thereby enhancing the optical absorption by the QDs. Based on the simulation of the model structure, Ag nanoparticle array was formed on both the n-type GaAs substrate of the InAs/GaNAs QD solar cell and the semi-insulating GaAs substrate of the InGaAs/GaAsP MQW solar cell. Since n-type GaAs substrate has relatively large free carrier absorption coefficient in the longer wavelengths than 900 nm, the thick n-type substrate absorbed the near IR photons without current generation, resulting in energy loss of the photons. On the other hand, the reduction in free carrier in the substrate significantly improved the light trapping efficiency; the spectral response measurements revealed that Ag nanoparticles on the MQW cell with the semi-insulating substrate, which shows less free carrier absorption, improved photocurrent of the cell near the IR range. The correlation between the metal nanostructures and the light trapping efficiency of the cell will be investigated.
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