成果報告書詳細
管理番号20160000000286
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(低コスト化技術・量子ドット成長技術)」
公開日2016/12/14
報告書年度2015 - 2015
委託先名国立研究開発法人産業技術総合研究所
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 (Technologies for cost reduction and quantum dot growth) (FY2015-FY2017) FY2015 Annual Report

In FY2015, we have achieved a III-V/Si smart stack solar cell with an efficiency of 23.2%. We also examined low concentration smart stack cells which have a practical solution to consist with high efficiency and low cost. As a result, we obtained a GaAs/CIGSe 3-junction solar cell with a maximum conversion efficiency of 25.3% at 5.7 suns, which is the record value for a two-terminal III-V/CIGSe solar cell. For the top cells of smart stack multijunction cells, we investigated InGaAsP (1.65eV) solar cells on GaAs substrates and obtained high quality InGaP/InGaAsP/GaAs 3 junction top cells with the high Voc of 3.16 V fabricated using solid-source MBE for the first time. We also investigated InP-based inverted solar cells with 1.05 eV bandgap for smart stack bottom cells for the first time. The inverted InGaAsP solar cells shows superior Voc of 0.60 V compared with that of 0.54 V for the upright cell processed due to the reduction of dark current. As a target form of the large-area smart stacking, cells/modules consisting of many pieces of epitaxially lifted-off (ELO) thin films (top cells, size: 5-20 mm) arrayed on a large-area substrate (bottom cell, size: 3-6 inch) is envisioned. To this end, we developed a handling technique for fragile ELO thin films using organic materials as tentative supports. As a result, the process yields of the smart stack are greatly enhanced. For the evaluation of device lifetime, temperature cycling tests were performed. No obvious degradation was observed with III-V/Si smart stack cells. Quantum-dot-based intermediate band solar cells (IBSCs) have attracted significant attention as a means of exceeding the performance of single-junction solar cells. As a novel approach toward achieving efficient IBSCs, we focus on type-II InP QDs in an InGaP host. From time-resolved PL spectroscopy, carrier lifetimes greater than 30 ns are demonstrated, which presents the longest carrier lifetime in type-II QDs in wide-bandgap host semiconductors. This indicates that type-II InP QDs can simultaneously suppress thermal carrier escape while enhancing the second optical excitation in the InGaP host, thus leading to a highly efficient IBSC. We also investigated the carrier dynamics on multi-stacked type-II Ge/Si QDs. We successfully developed 100-layers-stacked Ge QDs grown on Si substrates by MBE. The time-resolved PL showed the extremely long carrier lifetime of longer than 100 ns for Ge QDs. We observed the obvious increase in the EQE in longer wavelength region up to 1300 nm due to the contribution from the photo-absorption in Ge/Si QD cells. Furthermore, the EQE response in longer wavelength region was increased by the irradiation of infra-red (IR) bias possibly due to the two-step photon absorption processes.
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