聚(3-己基)噻吩薄膜中电荷传导的研究

A Charge Transport Study on Thin Films of Poly(3-hexylthiophene)

对两种具有相同化学结构的聚(3-己基)噻吩膜进行了电荷传导研究以检验膜的结构对载流子迁移率的影响.一种膜是由3-己基噻吩单体经电化学合成直接制备的膜(原位生长膜);另一种膜是将原位生长膜溶于三氯甲烷后重新滴涂而成的(滴涂膜).研究表明,虽然两种膜的制备方法不一样,但在最低(0.02%)和较高(20%～30%)掺杂率下两膜中的载流子迁移率相一致;然而在中等掺杂率区域,两膜中的载流子迁移率明显不同.对于原位生长膜,载流子迁移率在低掺杂区域几乎保持不变,当掺杂率大于1%后开始上升;而在滴涂膜中,随着掺杂率的增加,迁移率先下降然后迅速升高.上述两种迁移率变化特征分别与以前研究中观察到的电化学合成高分子膜和化学合成高分子旋涂或滴涂膜中迁移率的变化特征相一致,表明了迁移率随掺杂率变化特征的改变是由膜的结构变化而引起的.

Two kinds of poly（3-hexylthiophene） films with the same chemical compositions were subjected to a charge transport study in order to examine possible influences of film structures on mobilities of charge carriers. One film was electrochemically synthesized using 3-hexylthiophene as a monomer （as-grown film）, and the other was prepared by dissolving the as-grow film in chloroform and then cast the polymer solution （cast film）. Mobilities coincided well at the lowest （0.02%） and high （20%~30%） doping levels, irrespec- tive of the film preparation methods. However, a clear difference was found between the two kinds of poly- mer films in the intermediate doping region. The mobility for the as-grown film was almost constant in the low doping region and then started to increase at 1% doping level, whereas the mobility for the cast film showed an initial decrease followed by a drastic increase with the doping level. These features of doping level vs. mobility plots are consistent with those observed earlier with electrochemically generated polythiophene and poly（3-methylthiophene） films and cast films of chemically synthesized poly（3-hexylthiophene）s and poly（3-octylthiophene）s. This finding demonstrates that the above features originate solely from the difference in structures of the polymer films.