有机半导体在电场下的极化作用及光电器件的原位拉曼成像

The three-dimensional distribution and evolution of the potential and carrier in the working conditions of the device are of great significance to the design of new materials and the optimization of the fabrication process. Raman spectra are normally used to characterize chemical structures, where Raman activity is determined by the molecular polarizability. Under the electric field (or current), the molecule would be polarized, which also induced change the dipole polarizability. Thus without obvious molecular structural change, the electric field can induce the obvious change of Raman spectroscopy, where the electric field change and distribution have a clear quantitative relationship with spectral changes. This project intends to realize high sensitivity steady-state measurement of working process in photoelectric device by this principle, which would relate to the scientific problems in the mechanism of organic optoelectronic devices. We plan to use field-effect transistor as the basic device structure, with the active layer of typical electron/hole transporting materials, pentacene and perylene bisimide. The project would combine with molecular structure change and electric-field induced molecular polarizability change, by surface enhanced Raman imaging technology, spectrum analysis and theoretical simulation, which realize direct observation of potential distribution in the conducting channel under different grid voltage by Raman peak intensity change and peak shift. These results would be further extended to other planar and vertical photoelectric device, which assistant the visualization of internal electric field and device mechanism research.

在器件工作条件下电势和载流子的三维分布及其演化过程，对新材料的设计与器件制备过程的优化有着重要意义。拉曼光谱通常用于表征化学结构的变化；但原理上拉曼活性是由分子极化率决定的。在电场（或电流）作用下，分子发生极化，因此即使分子结构变化不大，电场诱导的偶极和极化率改变也可引起拉曼光谱的明显变化，并且光谱变化与电场及载流子密度存在明确定量关系。本项目拟利用这一原理实现光电器件工作过程的高灵敏度稳态测量。针对有机光电器件机理研究的关键科学问题，以有机场效应晶体管为基本器件结构，以并五苯，苝酰亚胺等典型的电子空穴材料为活性层，本项目拟结合分子结构变化和场致分子极化率的变化，通过表面增强原位拉曼成像技术、光谱解析与理论模拟，观察不同栅压下导电沟道拉曼峰强度峰位变化，实现对场效应管沟道压降分布的直接观察，并进一步拓展到基于其他高性能材料体系的平面型和垂直型光电器件的内电场可视化和机理研究。

在器件工作条件下电势和载流子的三维分布及其演化过程，对新材料的设计与器件制备过程的优化有着重要意义。本项目利用分子极化和电场的定量关系，实现光电器件工作过程的高灵敏度稳态测量。针对有机光电器件机理研究的关键科学问题，以有机场效应晶体管为基本器件结构，结合分子结构变化和场致分子极化率的变化，通过表面增强原位拉曼成像技术、光谱解析与理论模拟，实现对场效应管沟道压降分布的直接观察，并进一步拓展到基于其他高性能材料体系的平面型和垂直型光电器件的内电场可视化和机理研究，实现了国际首次德拜屏蔽层厚度的实验测量，超高分辨像素的边缘效应分析，不同器件结构的电位分布原位观察等常规方法难以实现的实验观察。原位的器件机理研究，为器件的结构优化提供了很好的指导，并大大加快了器件结构优化的速度，申请人正在积极组织对于器件结构的分析进行规范化和程序化，使本项目的研究结果为更多的研究人员服务。