Photoexcited charge collection spectroscopy of two-dimensional polaronic states in polymer thin-film transistors
Photoexcited charge collection spectroscopy of two-dimensional polaronic states in polymer thin-film transistors
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DOI：
10.1103/physrevb.85.045206
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发表时间：
2012-01-17
影响因子：
3.7
通讯作者：
Im, Seongil
中科院分区：
文献类型：
--
作者：
Lee, Jiyoul;Lee, Bang-Lin;Im, Seongil
利用新开发的原位光激发电荷收集光谱（PECCS）研究了可完全工作的噻吩基薄膜晶体管（TFT）中聚合物半导体块体或聚合物半导体-电介质界面中与链间堆积相关的极化子结构。聚合物半导体的原位PECCS光谱在2.05 - 2.45 eV之间显示出pi-pi* 吸收峰，这与相应聚合物薄膜的紫外-可见（UV-vis）吸收光谱中的吸收峰匹配良好。光谱还显示在低于pi-pi* 吸收边1.32、1.39、1.58和1.71 eV处的相关电荷诱导吸收峰。这些电荷诱导吸收峰可能与位于聚合物半导体体和我们的聚合物基TFT的半导体-电介质界面的离域极化子态有关。从光谱结果，我们能够提取的极化态密度（DOS）的聚合物通道，我们证实，在聚合物半导体通道中的密集的链间包装导致更大的DOS附近的带边，从而导致更高的场效应迁移率。
The polaronic structures associated with the interchain stacking in the polymer semiconductor bulk or polymer semiconductor-dielectric interface in fully operational thiophene-based thin-film transistors (TFTs) were investigated with a newly developed in situ photoexcited charge collection spectroscopy (PECCS). The in situ PECCS spectra of polymer semiconductors exhibited the pi-pi* absorption peaks between 2.05 and 2.45 eV, which were well-matched with those in the Ultraviolet-visible (UV-vis) absorption spectra of the corresponding polymer films. The spectra also showed associated charge-induced absorption peaks at 1.32, 1.39, 1.58, and 1.71 eV below the pi-pi* absorption edge. These charge-induced absorption peaks might be related to the delocalized polaron states located in the both polymer semiconductor bulk and semiconductor-dielectric interface of our polymer-based TFTs. From the spectral results, we were able to extract the polaronic density of states (DOS) of the polymer channel, and we confirmed that the denser interchain packing in the polymer semiconductor channel leads to a larger DOS near the band edge, resulting in higher field-effect mobility.