成果報告書詳細
管理番号20110000000777
タイトル*平成22年度中間年報 太陽エネルギー技術研究開発 太陽光発電システム次世代高性能技術の開発 三層協調界面構築による高効率・低コスト・量産型色素増感太陽電池の研究開発(高効率化技術及びメカニズム解析に関する研究開発)
公開日2011/8/5
報告書年度2010 - 2010
委託先名国立大学法人信州大学
プロジェクト番号P07015
部署名新エネルギー部
和文要約素増感太陽電池の高効率化技術、低コスト化技術、量産化技術、信頼性向上技術に関する技術開発を実施するにあたって、色素増感太陽電池の三層(酸化物半導体、色素、電解質)に注目し、それらの材料開発、光電変換現象、劣化機構の解析をおこなうとともに、それらを反映した高効率セル及びモジュールの試作・評価、信頼性に関する評価をおこなう。本事業では高効率化技術及びメカニズム解析に関する研究開発を進める。
1.反応エネルギー制御色素の開発
これまでに最も高い変換効率を持つBlack Dye(変換効率11.2%)の分子構造最適化による高効率化を目指した。逐次的な縮合反応を利用して配位子合成をおこない、新規ルテニウム錯体を合成した。合成したルテニウム錯体の溶液内での吸収スペクトルは、既報のBlack Dye(N749)と比較して各吸収ピークの長波長側へのシフトが見られ、置換基導入によるBlack Dyeの長波長化に成功した。今後構造最適化によってBlack Dye を凌駕する色素の創成を進める。
2.高効率小型セルの開発
22年度においては、既存の材料を用いて電荷分離過程の評価を行った。材料を変えて注入効率と還元効率を評価した結果、酸化チタン材料によって注入効率が異なることなどが判明し、開放電圧向上の可能性があることが分かった。今後はこれらの決定因子について解明する。
英文要約Title: Research and development of high-efficiency and low-cost dye-sensitized solar cells and their mass production technologies based on the three phase-harmonized interface (FY2010-2012) FY2010 Annual Report
Objects of the project.: A new series of ruthenium(II) sensitizers for dye-sensitized solar cells (DSSCs) derived from asymmetric terpyridyl complexes possessing different substituents on each pyridine in terpyridine ligand have been developed. Novel asymmetric terpyridine ligands were synthesized from acetylpyridine derivatives as starting materials through two synthetic steps and the target ligands were yielded in 40 % overall yield. The synthesized ligands have one or two carboxylic acids as an adsorption site on the surface of TiO2 nanoparticles and various kinds of substituent can introduce into the other pyridine segments in the terpypyridine ligand. The newly synthesized ruthenium complexes MJ-2 and MJ-3 exhibited similar absorption spectra as black dye (N749). The MLCT band for MJ-3 was red-shifted by 40 nm and the Ru (II)/Ru(III) oxidation potential of MJ-3 shifted cathodically compared with N749. Thus, the introduction of substituent into the terpyridine ligands can tune absorption spectra and redox potentials of ruthenium complexes. The red-shifts of absorption spectra and the tuning of redox potentials will open up the way to improve the overall efficiency of DSSCs. While the synthesized dyes MJ-2 and MJ-3 were adsorbed in nanocrystalline TiO2 porous films show slightly lower efficiencies than N749, the IPCE of MJ-3 in the near-IR region is higher than N749.
To increase the energy conversion efficiency, materials will be developed based on following four categories, 1:semiconductor enabling high injection efficiency from dye, 2:dye with high injection efficiency, 3:dye with high reduction efficiency, and 4:redox couple or hole transport materials with high reduction efficiency. For the semiconductor, we compared TiO2 nano-particles supplied by Solaronix and that synthesized by Sumitomo Osaka Cement (SOC). It was found that the TiO2 by SOC has less charge trap density, suggesting higher crystallinity. As for dye-sensitized solar cells, TiO2 by SOC showed higher short-circuit current per amount of adsorbed dyes. This implies that the TiO2 by SOC has higher injection efficiency.
For injection, to elucidate the relationship between dye structures and injection efficiency, we measured external quantum efficiency (IPCE) with the combination of dyes with various LUMO potentials and electrolytes with different amount of LiI. The plot of IPCE as a function of free energy difference showed that coumarine dyes required larger energy difference than carbazole dyes.
For reduction, the Ru dye (MJ-3) has HOMO potential at more positive values than that of N719. The reduction efficiency was estimated with electrolyte containing various I- concentrations. In comparison to commonly used Ru dye (N719), MJ-3 required more I- concentrations, implying that the reduction efficiency is lower than N719.
Another way to decrease free energy difference for dye cation reduction is employing different redox couples or hole transport materials. We examined Br-/Br3- redox couple and P3HT with various dyes.
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