Molecular semiconductors: Terahertz spectroscopy of charge transport on the nanoscale

分子半导体：纳米级电荷传输的太赫兹光谱

• 批准号: 420459768
• 负责人: Professor Dr. Roland Kersting
• 金额: --
• 依托单位: Lehrstuhl für Photonik und Optoelektronik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/420459768?language=en
• 关键词: Molecular; semiconductors; Terahertz; spectroscopy; charge

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.

在过去的二十年里，有机场效应晶体管 (OFET) 的发展使首次应用成为可能。然而，薄膜 OFET 获得的迁移率收敛于约 10 cm2/Vs 的值，这对于许多应用来说可能不够。此外，对载流子传输的基本理解尚未达到无机半导体已知的水平。通过拟议的研究，我们希望阐明预计会减慢分子半导体传输速度的两个过程。这些是导致极化子和电荷动态局域化的载流子-声子相互作用。极化子和动态局域化都可以在 OFET 的通道内有效地筛选，这应该会导致自由载流子和类似布洛赫的运输。为了了解载流子传输的这些基本特性，我们将进行太赫兹（THz）传输实验，以探测纳米尺度上的局部传输，并且不受晶界或其他外在参数的影响。从太赫兹数据中，可以获得载流子的有效质量及其散射时间。它们的温度依赖性将显示极化子的形成和动态局域化如何影响传输。特别令人感兴趣的是这些过程在一定密度下被电荷载流子屏蔽的程度，这对于 OFET 的反型层来说是典型的。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显着飞跃，使 OFET 更接近应用。