Organic Materials & Devices (OMD), Dept. of Materials Science, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) , Martensstraße 7, 91058 Erlangen, Germany.
Computer-Chemie-Centrum and Interdisciplinary Center for Molecular Materials, FAU , Nägelsbachstraße 25, 91052 Erlangen, Germany.
ACS Nano. 2017 Sep 26;11(9):8747-8757. doi: 10.1021/acsnano.7b02394. Epub 2017 Aug 18.
Self-assembled monolayer field-effect transistors (SAMFETs) are not only a promising type of organic electronic device but also allow detailed analyses of structure-property correlations. The influence of the morphology on the charge transport is particularly pronounced, due to the confined monolayer of 2D-π-stacked organic semiconductor molecules. The morphology, in turn, is governed by relatively weak van-der-Waals interactions and is thus prone to dynamic structural fluctuations. Accordingly, combining electronic and physical characterization and time-averaged X-ray analyses with the dynamic information available at atomic resolution from simulations allows us to characterize self-assembled monolayer (SAM) based devices in great detail. For this purpose, we have constructed transistors based on SAMs of two molecules that consist of the organic p-type semiconductor benzothieno[3,2-b][1]benzothiophene (BTBT), linked to a C or C alkylphosphonic acid. Both molecules form ordered SAMs; however, our experiments show that the size of the crystalline domains and the charge-transport properties vary considerably in the two systems. These findings were confirmed by molecular dynamics (MD) simulations and semiempirical molecular-orbital electronic-structure calculations, performed on snapshots from the MD simulations at different times, revealing, in atomistic detail, how the charge transport in organic semiconductors is influenced and limited by dynamic disorder.
自组装单分子层场效应晶体管（SAMFET）不仅是一种很有前途的有机电子器件，还允许对结构-性能相关性进行详细分析。由于二维π堆叠有机半导体分子的受限单分子层，电荷输运对形态的影响尤为显著。而形态又受到相对较弱的范德华相互作用的控制，因此容易发生动态结构波动。因此，将电子和物理特性分析以及时间平均 X 射线分析与来自模拟的原子分辨率的动态信息相结合，使我们能够非常详细地对自组装单分子层（SAM）基器件进行表征。为此，我们构建了基于两种分子的 SAM 的晶体管，这两种分子由有机 p 型半导体苯并噻吩[3,2-b][1]苯并噻吩（BTBT）与 C 或 C 烷基膦酸相连。这两种分子都形成了有序的 SAM，但我们的实验表明，两个体系中晶体畴的大小和电荷输运性能有很大差异。这些发现得到了分子动力学（MD）模拟和半经验分子轨道电子结构计算的证实，这些模拟和计算是在不同时间从 MD 模拟的快照上进行的，详细揭示了有机半导体中的电荷输运如何受到动态无序的影响和限制。
