成果報告書詳細
管理番号20110000000599
タイトル*平成22年度中間年報 最先端研究開発支援プログラム/低炭素社会に資する有機系太陽電池の開発/光電変換の原理解明に基づく高効率有機薄膜太陽電池の開発
公開日2011/7/28
報告書年度2010 - 2010
委託先名国立大学法人京都大学
プロジェクト番号P09026
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 サブテーマ(8) (8)-1 高効率有機薄膜太陽電池のための材料開発 (平成22年度第1四半期~第4四半期実施) 高効率化の目標を達成するため、平成22年度は、新規な近赤外色素と近赤外共役高分子の設計・合成に取り組んだ。近赤外色素は、高分子・フラーレンブレンド膜に第3成分として、色素分子を導入することにより光捕集帯域の向上を目指すものである。したがって、色素分子を凝集することなく高分子・フラーレンヘテロ接合界面へと自発的に偏在させることが鍵となる。
英文要約Funding Program for World-Leading Innovative R&D on Science and Technology / Development of Organic Photovoltaics toward a Low-Carbon Society / Development of Highly Efficient Organic Solar Cells Based on Photovoltaic Conversion Mechanism
(FY2010-FY2011) FY2010 Annual Report
VIII-1. New Materials for Highly Efficient Organic Solar Cells
(From the first quarter to the fourth quarter of 2010)
In 2010, we have newly synthesized near-IR dye molecules and low-bandgap conjugated polymers for highly efficient organic solar cells. We have previously demonstrated that the light-harvesting efficiency of organic solar cells based on a blend of poly(3-hexylthiophene) (P3HT) and a fullerene derivative (PCBM) can be substantially improved by the incorporation of near-IR dyes that have absorption bands at wavelengths longer than the original materials of P3HT and PCBM. As a result, we found two keys to the improvement: 1) preventing dye aggregation in blend films and 2) selective loading of dye molecules at the polymer/fullerene interface. In order to clarify how large bulky substituents can prevent dye from aggregation, we systematically synthesized several silicon phthalocyanine derivatives with different axial ligands (SiPcn) as shown in Fig. 1. For P3HT/PCBM/SiPc2 solar cells, no dye sensitization effect was observed because of the significant decrease in the absorption of SiPc2 in the blend. For P3HT/PCBM/SiPcn (n ~ 3) solar cells, on the other hand, distinct dye sensitization effect was observed at the dye absorption band. In particular, the improvement in the photocurrent was maximum at n = 4 and 6. For P3HT/PCBM/SiPc6 solar cells, fill factor slightly decreased, suggesting that longer substituents suppress the charge transport. We therefore conclude that the appropriate length of alkyl substituents in axial ligands to SiPc is 4 to 6, which can effectively prevent dye molecules from π stacking and keep the intermolecular interaction for the charge transport.
VIII-2. Transient Absorption Spectroscopy in Organic Solar Cells
(From the second quarter to the fourth quarter of 2010)
In 2010, we have set up new transient absorption spectroscopy system for studying photovoltaic conversion processes in organic solar cells. As scheduled, the new system was installed in the fiscal year. In parallel with the installation, we studied the photosensitization mechanism in P3HT/PCBM solar cells incorporating near-IR dye molecules. Upon the excitation of dye in P3HT/PCBM/SiPc ternary blend films, polymer polaron and dye anion was promptly generated in a few picoseconds followed by the efficient charge shift from SiPc anion to PCBM on a timescale of tens picoseconds. These dye sensitization processes as shown in Fig. 2 are two orders of magnitude faster than the corresponding back recombination processes, suggesting that all the processes proceed with 100% efficiency. We therefore conclude that our approach can easily expand the absorption range efficiently.
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