Photoconductivity in organic thin films: From picoseconds to seconds after excitation
Photoconductivity in organic thin films: From picoseconds to seconds after excitation
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DOI：
10.1063/1.2946453
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发表时间：
2008-06-15
影响因子：
3.2
通讯作者：
Ostroverkhova, O.
中科院分区：
文献类型：
--
作者：
Day, J.;Subramanian, S.;Ostroverkhova, O.
我们在皮秒到秒的时间尺度上详细研究了溶液生长的功能化并五烯（Pc）、蒽噻吩（ADT）和二氰亚甲基二氢呋喃（DCDHF）薄膜的瞬态和连续波（cw）光电性。在所有薄膜中，在285-350 K的温度下，我们观察到在皮秒时间尺度上的快速载流子光产生和非热激活电荷输运。室温光激发后约30 ps，外加电场为1.2x10(4) V/cm时，adt -三异丙基乙炔基-(TIPS)- f、Pc-TIPS和DCDHF薄膜的迁移率和光发生效率乘积mu eta分别为0.018-0.025、0.01-0.022和0.002-0.004 cm(2)/V s，取决于薄膜质量，且与弱电场相关。在功能化的ADT和Pc薄膜中，在最好的样品中，在光激发后的时间尺度上，可以观察到瞬态光电性的幂律衰减动力学。相比之下，在DCDHF非晶玻璃中，大多数光生载流子被困在类似200 ps的范围内。光激发载流子在更长的时间尺度上的输运是通过一个可变斩波频率的光学斩波器连续波照射来探测的。与在皮秒时间尺度上观察到的情况相反，在毫秒和更长时间尺度上的载流子主要是局域化的，其特点是载流子寿命分布广泛。这类载流子对直流光导电性作出了主要贡献。(C) 2008年美国物理研究所。
We present a detailed study, on time scales from picoseconds to seconds, of transient and continuous wave (cw) photoconductivity in solution-grown thin films of functionalized pentacene (Pc), anthradithiophene (ADT), and dicyanomethylenedihydrofuran (DCDHF). In all films, at temperatures of 285-350 K, we observe fast carrier photogeneration and nonthermally activated charge transport on picosecond time scales. At similar to 30 ps after photoexcitation at room temperature and at applied electric field of 1.2x10(4) V/cm, values obtained for the product of mobility and photogeneration efficiency, mu eta, in ADT-tri-isoproplysilylethynyl-(TIPS)-F, Pc-TIPS, and DCDHF films are similar to 0.018-0.025, similar to 0.01-0.022, and similar to 0.002-0.004 cm(2)/V s, respectively, depending on the film quality, and are weakly electric field dependent. In functionalized ADT and Pc films, the power-law decay dynamics of the transient photoconductivity is observed, on time scales of up to similar to 1 mu s after photoexcitation, in the best samples. In contrast, in DCDHF amorphous glass, most of the photogenerated carriers are trapped within similar to 200 ps. Transport of photoexcited carriers on longer time scales is probed by cw illumination through an optical chopper, with a variable chopper frequency. In contrast with what is observed on picosecond time scales, charge carriers on millisecond and longer time scales are predominantly localized, and are characterized by a broad distribution of carrier lifetimes. Such carriers make the principal contributions to dc photoconductivity. (C) 2008 American Institute of Physics.