成果報告書詳細
管理番号20140000000593
タイトル*平成25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) 低倍率集光型薄膜フルスペクトル太陽電池の研究開発
公開日2014/12/27
報告書年度2013 - 2013
委託先名国立大学法人東京工業大学
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: Thin Film Full Spectrum Solar Cells with Low Concentration Ratios (FY2008-FY2014) FY2013 Annual Report, Tokyo Institute of Technology

In order to realize thin-film solar cells with conversion efficiencies over 40%, we are developing novel absorber materials. (1)Si Based Thin Film Concentrators: To increase the performance of thin-film solar cells, solar spectrum splitting technique has been considered and studied. Up to now total efficiencies of about 22.9 % and 25.9% have been obtained for a-Si//CIGS and GaInP//CIGS configurations, respectively, at the splitting wavelength of 614 nm. It was also found from the simulation that a total efficiency of 30% can be obtained using GaInP, GaAs and CIGS with dual splitters. In order to optimize solar spectrum splitting system, spectrum splitting modules and two axes solar tracker were developed. Meteorological data obtained in Kisarazu were used for yield estimation of the spectrum splitting system. The defect in a-SiOX:H films has been evaluated. ESR spectra was composed of two spin signals with g-values of 2.005 (Si dangling bond) and 2.013. Photosensitivity decreased with increasing the spin density with g-value of 2.005. The obtained results suggested we needed to decrease the Si dangling bond density in order to improve the properties of a-SiOX:H films. Annual performance monitoring system was installed. This system tracks the sun autonomously, using 2 axis sun tracking system. Sunlight is concentrated by the optical lens with the concentration ratio of 6, and is split using the optical splitters. From the obtained results of short circuit currents and solar radiation intensities, it was found that the influence of the diffuse irradiance was extremely small in this PV system. (2) Chalcopyrite Based Thin Film Concentrators: Effects of the valence band offset between a CdS layer and a CIGS layer with energy bandgaps from 1.05 to 1.6 eV were theoretically investigated. It was found that an efficiency of 22% can be expected for the valence band offset of 0.3 eV with a band gap of 1.35 eV. An efficiency of 23.4% was theoretically achieved with a single-graded conduction band profile. Furthermore, we investigated the origin of low fill factors of Au(In,Ga)Se2 (AIGS) solar cells, and it was found that the low carrier concentration of AIGS layer is one of the causes for the low fill factors. In order to improve the fill factor of AIGS solar cells, the increase of carrier concentration or insertion of a thin heavily doped layer between AIGS and Mo have been proposed.
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