成果報告書詳細
管理番号20160000000187
タイトル*平成27年度中間年報 「高性能・高信頼性太陽光発電の発電コスト低減技術開発/革新的新構造太陽電池の研究開発/超高効率・低コストIIIーV化合物太陽電池モジュールの研究開発(高密度量子ドット成長技術)」
公開日2016/12/14
報告書年度2015 - 2015
委託先名国立大学法人電気通信大学
プロジェクト番号P15003
部署名新エネルギー部
和文要約
英文要約Title: Development of high performance and reliable PV modules to reduce levelized cost of energy Research and Development of innovative new structure solar cells Research and Development of ultra-high efficiency and low-cost III-V compound semiconductor solar cell modules (High density quantum dot growth technology) (FY2015-FY2017) FY2015 Annual Report

In the first year (2015) of this NEDO research project, our group of University of Electro-Communications developed in-plane ultrahigh-density InAs quantum-dots (QDs) and studied their optical properties and solar cell properties. The main results are described as follows.
(1) In the previous NEDO project, we developed in-plane ultrahigh-density InAs QDs with 1.0 ×1012 cm-2 on InAsSb/GaAs(001). In order to clarify the mechanism of high-density 3-dimensional (3D) nucleation, we studied the InAs growth process on InAsSb/GaAs(001) by RHEED and AFM observations. We found the narrowing of 2D islands and a multi-nucleation mode of 3D islands because of the excess strain. These results will provide valuable information for increasing more the QD density.
(2) Long carrier lifetime in the QDs is one of important characteristics to enhance two-step photo-excitation effect. A type-II band structure of ultrahigh-density InAs QDs with a GaAsSb capping layer was fabricated, and their optical properties were studied. In-direct and direct transitions were analyzed in PL spectra. At low temperature below 80 K, in-direct transition having a long PL decay time was dominant. As the temperature increased, the direct transition became stronger than in-direct transition.
(3) To improve a crystal quality of in-plane ultrahigh-density InAs QDs, the QD sample was thermally annealed. After the annealing, the PL intensity increased and the PL decay time was slightly increased because of suppression of non-radiative recombination centers. The GaAs solar cells including the in-plane ultrahigh-density InAs QDs were fabricated, and their external quantum efficiency and I-V properties under light irradiation (AM1.5, 1 sun) were improved by the thermal annealing.
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