Bimodal Polarons and Hole Transport in Poly(3-hexylthiophene):Fullerene Blend Films

被引:117
作者
Guo, Jiamo [1 ]
Ohkita, Hideo [1 ,2 ]
Yokoya, Seiichirou [1 ]
Benten, Hiroaki [1 ]
Ito, Shinzaburo [1 ]
机构
[1] Kyoto Univ, Dept Polymer Chem, Grad Sch Engn, Nishikyo Ku, Kyoto 6158510, Japan
[2] Japan Sci & Technol Agcy JST, PRESTO, Kawaguchi, Saitama 3320012, Japan
关键词
POLYMER SOLAR-CELLS; CHARGE RECOMBINATION; POLYTHIOPHENE; GENERATION; MORPHOLOGY; EFFICIENCY; COMPOSITE; DYNAMICS; CARRIERS; VOLTAGE;
D O I
10.1021/ja9108787
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The bimolecular recombination dynamics in blend films of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) has been studied by transient absorption spectroscopy. On a microsecond time scale, two polaron bands were observed at 700 and 1000 nm and exhibited different bimolecular recombination dynamics. The 700-nm band decayed with a time-independent bimolecular recombination rate of 10(-12) cm(3) s(-1). The activation energy was as small as similar to 0.078 eV independently of the carrier density. On the other hand, the 1000-nm band decayed with a time-dependent bimolecular recombination rate, which varied from 10(-12) to 10(-13) cm(3) s(-1), depending on time or carrier density. The activation energy decreased exponentially from 0.178 to 0.097 eV with the increase in the carrier density. Therefore, we assigned the 700-nm band to freely mobile delocalized polarons in crystalline P3HT domains and the 1000-nm band to localized polarons trapped in relatively disordered P3HT domains. At a charge density of 10(17) cm(-3), which corresponds to 1 sun open-circuit condition, some localized polarons exhibited trap-free bimolecular recombination due to trap-filling. These findings suggest that not only delocalized polarons but also some localized polarons play a crucial role in the efficient hole transport in P3HT:PCBM solar cells.
引用
收藏
页码:9631 / 9637
页数:7
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