有机电子器件界面活性层的趋向性之和频振动光谱研究

Organic semiconductor devices have attracted much attention due to their potentially low cost and feasibility for large-area flexible devices. However, the poor stability strongly hinders their practical application. The irreversible evolution of interface morphology is a key reason for the degradation of molecular functional devices. Interface formed by organic semiconductor (OS) and alkyl molecule self-assembled monolayer (SAM) is often involved in organic field-effect transistors (OFETs). Our previous studies on some typical OFET devices show that the change of the conformation and orientation of the interfacial molecules is the main reason for the substantial decay of the electron mobility upon long-term storage. In this project, we propose to use in-situ and ex-situ sum frequency generation vibrational spectroscopy to　characterize a series of OS/SAM interfaces with different components. In combination with electronic analysis and molecular dynamics simulations, we will gain deep insights into the evolution tendency of the interfacial active layer and the physical mechanism lying behind. Specifically, we will investigate the effects of the surface coverage, alkyl chain length, and degree of fluorination of the SAM molecules, as well as the effects of the OS molecular structure and film preparation technique, on the assembling manner of the interfacial molecules and on the stability of the assembly. The purpose is to depict the micro/nanoscopic interfacial stress as a function of the local interfacial structure. This study will help to establish a universal physical model to explain the instability of organic interfaces, which will be of great value for the research field of all devices based on molecular materials.

有机半导体器件由于廉价、易实现大面积柔性器件等优点而备受人们关注，但稳定性差却严重阻碍了其大规模应用。界面形貌的不可逆演化是造成器件功能退化的重要因素。有机半导体（OS）/烷基分子自组装膜（SAM）界面是有机场效应管（OFET）器件中的常见界面。我们前期针对某些典型OFET器件的研究表明，界面分子的构象和取向变化是造成体系电子迁移率随时间衰减的主因。本项目中我们拟采用原位及非原位和频振动光谱技术，结合电子学测试和分子动力学模拟，对不同组分的OS/SAM界面进行系统性研究，深入探究界面活性层的趋向性和其物理机制。具体地，我们将通过考察烷基分子覆盖率、链长、氟代程度、端基，以及有机半导体分子结构和制膜工艺等因素对界面分子聚集状态及其稳定性的影响，揭示界面应力与界面微观结构之间的规律性关系。此研究有助于建立普适性的物理模型来解释有机界面的不稳定性，对所有分子材料器件的研究都将具有重要的参考价值。

有机半导体器件由于廉价、易实现大面积柔性器件等优点而备受人们关注，但稳定性差却严重阻碍了其大规模应用。界面形貌的不可逆演化是造成器件功能退化的重要因素。有机半导体（OS）/烷基分子自组装膜（SAM）界面是有机场效应管（OFET）器件中的常见界面。我们前期针对某些典型OFET器件的研究表明，界面分子的构象和取向变化是造成体系电子迁移率随时间衰减的主因。在本项目中，我们采用原位及非原位和频振动光谱技术，对不同有机半导体器件的OS/SAM界面进行系统性研究，深入探究了界面活性层的趋向性和其物理机制。具体地，我们已经证实了有机分子在钙钛矿有机电子器件表面的有序组装排列，是其界面偶极层形成的关键；研究了共轭分子在 ITO 玻璃表面的自组装过程，结果表明随着分子锚定密度的增大，其共轭单元的取向有序化要相对迟滞于锚定基团的有序化，而更强的锚定作用更有利于共轭分子的有序排列，构建更有效的空穴传输层；揭示了双官能团分子3-氯苄氨（3Cl-BA）本身在ZnO上的化学吸附并不具有单一取向性，这种取向性的组装行有利于钙钛矿薄膜的有序化生长；证实了在有机场效应半导体材料界面存在一种新型的分子构象诱导的界面应力，证明了该应力是材料老化和器件性能衰减的主要内在原因，深化了对有机场效应半导体材料与器件稳定性的认知，为提升器件稳定性提供了理论支撑。本研究工作建立的普适性物理模型可以解释有机界面的不稳定性，对所有分子材料器件的研究具有重要的参考价值。