Optical pump-probe spectroscopy of photocarriers in rubrene single crystals
Optical pump-probe spectroscopy of photocarriers in rubrene single crystals
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DOI：
10.1103/physrevb.83.075204
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发表时间：
2011-02
影响因子：
3.7
通讯作者：
S. Tao;H. Matsuzaki;H. Uemura;H. Yada;T. Uemura;J. Takeya;T. Hasegawa;H. Okamoto
中科院分区：
文献类型：
--
作者：
S. Tao;H. Matsuzaki;H. Uemura;H. Yada;T. Uemura;J. Takeya;T. Hasegawa;H. Okamoto
红荧烯是一种有机分子半导体，通过瞬态吸收光谱在宽能量范围（0.1 - 2.2 eV）内研究了其光生载流子动力学。通过光辐射，我们观察到三种吸收带在红外区，这是由于激子，自由载流子和极化子的诱导吸收。结果表明，当能量高于102.7eV（比最低激子能量高出104 eV）时，光辐照后立即产生自由载流子。这些自由载流子中的一些被稳定为极化子，而其他的被弛豫为激子。对于最低激子的共振激发，激子也可以产生极化子。极化子衰减动力学的温度依赖性表明，极化子迁移率随温度降低而增加，表明大极化子的带状传输。在80 K以下，光生载流子被缺陷或杂质捕获，并且它们的衰减动力学由从陷阱的逃逸时间主导。
The photocarrier dynamics of rubrene, an organic molecular semiconductor, are investigated by transient absorption spectroscopy over a wide energy range (0.1−2.2 eV). By photoirradiation, we observed three kinds of absorption bands in the infrared region, which are attributable to induced absorptions of excitons, free carriers, and polarons. The results show that for photoirradiation with energies higher than ∼2.7 eV (∼0.4 eV higher than the lowest exciton energy), free carriers are photogenerated just after the photoirradiation. Some of those free carriers are stabilized as polarons and the others are relaxed to excitons. For the resonant excitation to the lowest-exciton, polarons can also be generated from the excitons. The temperature dependence of the decay dynamics of polarons reveals that polaron mobility increases with decreasing temperature, indicating bandlike transport of large polarons. Below 80 K, photocarriers are trapped by defects or impurities and their decay dynamics are dominated by the escape time from traps.