成果報告書詳細
管理番号20120000000786
タイトル*平成23年度中間年報 太陽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)/高効率集光型太陽電池セル、モジュール及びシステムの開発(日EU共同開発)/集光型太陽電池用量子・ナノ構造の創製及び評価解析技術の開発(WP2)
公開日2012/11/28
報告書年度2011 - 2011
委託先名国立大学法人東京大学
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
本研究では、セル変換効率45%以上を達成するための要素開発として、歪み補償・歪みバランス系の材料構成による集光型量子・ナノ構造3接合セル技術を開発するとともに、集光型量子・ナノ太陽電池・多接合セルの特性評価装置の開発を併せて行う。
英文要約Title:Ultra-high efficiency concentration photovoltaic’s (CPV) cells, modules and Systems WP2:Novel device technologies and quantum nanostructures for CPV (FY2011-FY2012) FY2011 Annual Report
(1) Quantum nanostructures for CPV The structure of multi-quantum well (MQW) solar cell to be fabricated has been finalized and we have started to grow samples using a planetary MOVPE reactor. Both a QW heterostructure with MQWs alone inserted in between confinement layers and a QW p-i-n solar cell which includes MQWs in the i-region have been prepared. During growth, in-situ monitoring of wafer curvature was performed and layer thicknesses were altered slightly from the designed structure to adjust for a drift in the curvature baseline.In intermediate band solar cells (IBSCs), quantum dots (QDs) should ideally be half-filled with electrons in order to maximize photocurrent generation by two-step photon absorption. We have grown QDSCs with doped QDs layers embedded in strain compensating matrix in order to control the quasi-Fermi level of intermediate QD states. Non-radiative recombination losses and dark current were reduced thereby increasing the short-circuit current density from 24.1 (nondoped) to 30.6 mA/cm2 (doped) measured at 1sun. We have also performed photo-reflectance measurements and testing of these QD cells under concentration and confirmed that QDs form IB states.(2) Characterization of quantum nanostructures for CPV Time-resolved photoluminescence (TRPL) measurements on QD samples were performed by using an ultrahigh-speed streak camera which detects luminescence signals in the infrared region at the repetition frequency of 20 MHz. The light source used was a mode-locked Ti:sapphire pulse laser. We have developed a technique to fabricate QD solar cells with direct doping of Si into InAs QDs in GaNAs strain-compensating matrix. The Si atoms were evenly incorporated into QDs during the assembling stage of growth such that a uniform array of partially-filled QDs has been obtained. QD solar cells with varying doping concentration of QDs have been grown. The TRPL data indicate an increasing PL decay time with increasing QD doping up to 5 electrons-per-QD. Further, the Si-doping of QDs dramatically enhances the PL intensity excited at the high energy. This arises from reduction of non-radiative recombination probability during thermalization of carriers generated by high-energy photons, and thus Si doping is very useful for reducing nonradiative recombination process in particular for hot carriers generated by high-energy photons. (3)Development of characterization equipment of CPV cells We have designed and finalized the basic specifications required for reliable characterization of CPV multi-junction tandem cells and quantum nanostructured cells. The spectral response will become measurable over a wide spectral range from 300 to 2500nm. Further, I-V curves and mapping of laser scanned current generation (LBIC) can be characterized for each individual subcell. (Management, report, public relations) To carry out effectively the project with profiting “synergy” effects based on the cooperation between Japan-EU consortiums, WP6 exploited various efforts:-establish the scheme to seize progress information and implement; propose simplified reporting system (semestrial report/management by Milestone/Deliverable) -hold regular meetings; not only Japan-EU joint meeting (2times/yr, settled under Coordination agreement for NGCPV), but also Japanese partners' general meeting (details on researches of each WPs have been smoothly shared by all partners via these meetings and the project's site) -push/motivate EU partners to achieve "Targets" obligated for the Japanese partners (under their contract with NEDO) -propagate projects' aim and importance of CPV concepts to public, for realization novel energy system; organize open seminars/round table discussions with special advisors etc.
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