结构可控的高有序有机半导体结晶薄膜的溶液法生长及应用

The morphology and structure of the organic thin films, such as crystalline quality, film constituents and film configuration, have great effects on the electronic properties of the films. So an important route to improve the performances of organic electronic devices is to control the films’ morphology and structure. Among them, realizing structure-controllable ordered crystalline thin films shows great importance for organic thin film transistors and gas sensors. Now structure-controllable ordered crystalline thin films can be fabricated by vacuum deposition but with high cost and technology limit. Though solution process has made great progress in ordered crystalline films fabrication, it is still a challenge to realize controlling the structure. Here we propose to construct structure-controllable ordered crystalline thin films by solution process with the technology called dip-coating, as well as modification and assembly process; and improve performances of organic thin film transistors and gas sensors based on such films. Our plan is as follows: First, we try to fabricate ordered organic crystalline films by dip-coating, and investigate the growth mechanism by researching the relationship between the film morphology and molecule structure and growth parameters; Then realize controllable structure by surface modulation, patterning and multi- constituents or multilayer film fabrication technologies based on the former ordered structure; Last we aim to modulate the films’ electronic properties by forming heterojunctions and doping with optimized film structure, and obtain high performance organic thin film transistors and gas sensors.

有机薄膜的形态结构，如结晶质量、薄膜组分、薄膜构型等，对薄膜的迁移率等电学特性有重要影响，因此提高有机电子器件的一个重要途径就是对薄膜形态结构进行调控，其中实现结构可控的有序结晶薄膜对提高有机薄膜晶体管以及气体传感器性能具有重要意义。目前结构可控高有序结晶薄膜可由真空蒸镀实现，但其成本和技术要求较高；而简易、低成本的溶液法近年来在制备有序结晶薄膜上取得进步，但实现结构可控尚有难度。本项目提出以浸渍涂膜法为基础，结合修饰组装等手段实现结构可控的有序有机半导体结晶薄膜，并构建高性能有机薄膜晶体管和气体传感器。方案是首先通过浸渍涂膜法生长有序结晶薄膜，并通过研究薄膜形态结构与分子结构、生长参数的关系探索生长机制；在此基础上通过表面修饰、图案化以及多组分多层膜技术等实现对薄膜结构的人为控制；最后在优化的薄膜结构基础上通过构建异质结、掺杂体系调控薄膜电学性能，实现高性能的有机薄膜晶体管和气体传感器。

有机薄膜的形态结构和界面电子结构对薄膜的电学性质以及器件的性能参数有重要影响，因此有效调控这两个因素是提高相关器件性能的重要途径。本项目以浸渍提拉法为主体，探索了溶液法生长高有序有机结晶薄膜的方法及其生长机理，并利用溶液生长法获得的有机结晶及自组装薄膜为模板层或修饰层调节上层有机薄膜的形态结构和界面电子结构，实现了高性能的有机电子器件：1) 利用浸渍提拉法在DTBDT-Cn系列分子上实现了高质量结晶薄膜，并研究了烷基侧链长度对薄膜形态、晶体结构和分子堆积的影响；在DTBDT-C6上获得了高取向且厚度可控的条带结晶薄膜，表现出系列分子中最好的晶体管性能；2）利用浸渍提拉法在正构烷烃Cn上实现了高质量结晶薄膜，特别是在C44上实现了大尺寸的单分子层有机二维晶体，在其上生长的pentacene分子具有更好的结晶质量，且场效应迁移率比非模板生长的薄膜提高一个量级；3）利用溶液滴涂法在HOPG和Au（111）表面形成了单层有序自组装膜，并且可以调控pentacene在单晶表面从平躺生长改变为直立生长；4）利用溶液法在SiO2表面修饰具有不同端基的自组装分子层，通过端基与半导体分子TIPS的界面电荷转移实现对半导体层界面电子结构的调控，进而获得了对薄膜的电学性质的调控，分别得到了迁移率在1 cm2/Vs以上的高迁移率场效应晶体管和灵敏度超过1000%/ppm的超灵敏NO2传感器。本项目探索了浸渍提拉法获取高质量结晶薄膜的制备方法和生长机理，为用此方法构建高性能有机光电器件提供了经验；获得了一批具有特殊形态或电学特性的有机结晶薄膜体系，构建了具有较高迁移率的有机场效应晶体管和超高灵敏度的有机气体传感器；提出的利用修饰层的界面掺杂效应调控半导体工作层初始电导来获得高灵敏度气体传感器的策略对于有机气体传感器的发展会有重要的启发