成果報告書詳細
管理番号20110000000757
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/電荷分離・輸送・貯蔵ポリマーの複合機能制御と新型湿式太陽電池の創出
公開日2011/6/29
報告書年度2010 - 2010
委託先名学校法人早稲田大学
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
1.1 研究開発の内容
レドックスポリマーに増感色素分子を組み込んだ複合系を対象として、光誘起電子移動とそれにともなう輸送現象の全容解明により、色素増感太陽電池の多様化に将来必須となる革新的な電荷分離・輸送・貯蔵ポリマーを創出することを目的としている。電気化学的に可逆な酸化還元を示すニトロキシドラジカル誘導体において、色素への電子注入が効率よく生起し、速い自己電子交換反応や物質拡散に基づく効率的な電荷輸送が可能となることを実証するとともに、酸化還元電位の制御により高い光起電力を発生することを示す。本年度は、長寿命ラジカル種であるニトロキシドラジカル誘導体を中心とした一連の有機レドックス分子を色素増感太陽電池における有機系メディエータとして適用し、有機ラジカル種の適用性を解明するとともに、色素増感太陽電池を試作した。メディエータ濃度や添加剤、吸着剤や色素の最適化により、有機レドックスを用いた色素増感太陽電池で変換効率5.5 %を達成した。
英文要約Title: Founding Program for World-Leading Innovative R&D on Science and Technology (FIRST program). Development of organic Photovoltaic toward a Low-Carbon Society: Sub-project No.4 “Charge-Separation, -Propagation, and Storage Functions of Redox Polymers and their Application to Photovoltaic Cells”(FY2010-FY2011) FY2010 Annual Report
 
In this project, Nitroxide radical derivatives (including polymer), such as 2,2,6,6-tetramethylpiperidine-1-oxy (TEMPO), TEMPO substituted polymer, and organic redox materials were applied to dye-sensitized solar cell (DSSC) as a redox mediator. The optimized DSSC utilizing the TEMPO mediator was accomplished higher photovoltaic performance than iodide mediator’s DSSC. The more reactive radical spices could be able to improve the performance. The summarized results were in following four items.

(1) Synthesis of organic redox materials (polymers) and dye-hybrid redox molecules.
Organic redox materials were synthesized for applying to DSSC as mediator and their redox potentials were controlled by molecular design. Radical polymers bearing TEMPO moiety in repeating units were designed and synthesized to fill up titania dioxide porous electrodes and combine the charge-storage property to DSSC. Moreover, the dye molecules substituted redox active moiety were also designed and synthesized as new material.

(2) High reactive redox mediator for DSSC
Azaadamantane-1-oyl (AZA) exhibiting very high reactivity and novel electrochemical properties due to lower steric hindrance than TEMPO was applied to DSSC as a mediator. The DSSC utilizing AZA accomplished the 3.1 % of power conversion efficiency, and the value was 1.5 times higher than that of DSSC using TEMPO or iodide mediator.

(3) Optimization of DSSC fabrication for improvement of photovoltaic performance
To achieve higher photovoltaic performance, the thickness of titania oxide (TiO2) film were optimized, and the dye molecules absorbing longer region of visible light was selected. The DSSC using TEMPO mediator was affected to TiO2 film thickness strongly. With the increase of the thickness, open-circuit voltage was decreased, and short circuit current density, fill factor, and ~ were remained unchanged. This undesired decrease tendency of Voc was only appeared TEMPO mediator, and this result implied the back electron transfer between TiO2 film to TEMPO was occurred more often in longer diffusion path of TiO2 film. The long-length absorption dyes were also applied to achieve higher current density. Indoline derivative dye, D205, was afforded the highest photovoltaic performance (5.5%) in TEMPO mediated DSSC.

(4) Influence of organic redox materials for open-circuit voltage
The DSSCs using series of organic redox mediators were fabricated, and measured their photovoltaic performance. These open-circuit voltages were increased according to the energy gap between TiO2 Fermi level and redox potential of mediators, and the plots for Voc vs. the redox potentials were shown apparent linearity.
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