Molecular semiconductors: Terahertz spectroscopy of charge transport on the nanoscale

在过去的二十年里，有机场效应晶体管（OFFERT）的发展带来了第一个应用。然而，在薄膜OFFE 2上获得的迁移率收敛于约10 cm 2/Vs的值，这对于许多应用可能是不够的。此外，对载流子输运的基本理解还没有达到无机半导体的水平。通过这项研究，我们希望阐明两个有望减缓分子半导体传输的过程。这些是载流子-声子相互作用，导致极化子和动态本地化的charges.The拟议的工作是刺激的洞察力，极化子和动态本地化可以有效地屏蔽内的通道OFFERS，这将导致自由载流子和布洛赫运输。为了获得载流子输运的这些基本特性，我们将进行太赫兹（THz）传输实验，探测纳米尺度上的局部输运，并且不受晶界或其他外部参数的影响。从太赫兹数据，载流子的有效质量，以及他们的散射时间，将获得。它们的温度依赖性将显示极化子的形成和动力学局域化如何影响输运。特别令人感兴趣的是，在何种程度上，这些过程被屏蔽的电荷载流子的密度，这是典型的反型层的OFFEX。预期的结果不仅具有根本意义，而且还可能刺激新型分子半导体的发展，并可能导致迁移率的重大飞跃，使OFFEX更接近应用。

Over the past two decades, the development of organic field-effect transistors (OFETs) brought first applications into reach. The mobilities obtained on thin-film OFETs, however, converged at values of about 10 cm2/Vs, which may not be sufficient for many applications. Additionally, the fundamental understanding of carrier transport has not reached the level known from inorganic semiconductors. With the proposed research, we want to shed light on two processes that are expected to slow down transport in molecular semiconductors. These are the carrier-phonon interaction that leads to polarons and the dynamic localization of charges.The proposed work is stimulated by the insight that both, polarons and dynamic localization may be efficiently screened within the channel of OFETs, which should lead to free carriers and Bloch-like transport. In order to access these fundamental properties of carrier transport, we will perform terahertz (THz) transmission experiments that probe the local transport on the nanoscale and are not affected by grain boundaries or other extrinsic parameters. From the THz data, effective masses of the carriers, as well as their scattering times, will be obtained. Their temperature dependencies will show how polaron formation and dynamic localization affect transport. Of particular interest is the extent to which these processes are screened by charge carriers at densities, which are typical for the inversion layer of OFETs. The expected results are not only of fundamental interest, but they also may stimulate the development of novel molecular semiconductors and may lead to a significant leap in mobilities that brings OFETs closer to application.