溶液法控制生长有机半导体单晶薄膜阵列及其晶体管特性研究

Organic thin film field-effect transistors (OFETs) offer several advantages such as low cost, solution processability, flexibility and rich sources of organic materials compared with their inorganic counterparts. Therefore, OFETs have been the subject of intensive academic and commercial attention as potential alternative in applications such as flexible circuits, display backplanes as well as sensors. Single-crystalline OFETs are believed to be the most promising OFETs because of their better performance and environmental stability compared with the amorphous and polycrystalline OFETs. More and more researches focus on single-crystalline OFETs. However, at present, although there are several methods to fabricate aligned organic single crystal films, most of these techniques are in the exploratory stage, the uniformity and reproducibility of the fabricated single crystal films are poor. Therefore, these methods are still not suitable for convenient, large-area commercial production. Based on this consideration, new techniques are still desirable. In this project, we proposed a novel crystal film depositing technology to produce highly aligned single crystal film arrays by controlling the solution evaporation process. Particularly, through controlling both the evaporation rate and evaporation direction to control the crystal orientation and growth direction, large area aligned single crystal film arrays can be achieved on many substrates at the same time. The method provides a low-cost，maneuverable technology which can be used in batch production. Furthermore we will reveal the influence of Evaporation-Induced Self Assembly Theory on the molecular packing and dynamic mechanisms of crystal growth. We will reach the achievement of high-performance organic thin film transistor arrays with the average mobility of 5 cm^2/V.s and over 60 percent coverage on the substrate. Finally, we will systematically investigate the stability of the single-crystal OFETs according to the response of the device to the environmental gases, pressure, temperature, light and electrical stress.

有机薄膜场效应晶体管（OFET）因半导体材料种类丰富、可常温制备而成为轻柔电子电路、显示驱动和传感的关键部件，在航空航天和军工领域有重要应用价值。有机单晶薄膜场效应晶体管因可有效解决非晶和多晶OFET面临的性能低、稳定性差的问题，已成为OFET的研究重点。目前，有效的大面积有机单晶薄膜制备方法少，工艺处于摸索阶段，单晶薄膜的均匀性和重复性远不能满足生产需要。本项目拟开发一种双重调控溶剂挥发方向和速率以实现有机半导体同时在多个基片上大面积取向为单晶薄膜阵列的新方法；探索基片表面能、溶液浓度、溶剂挥发方向和速率与单晶薄膜开始二维生长的临界状态之间的关系，建立挥发诱导分子自组装模型，为有机单晶薄膜生长提供理论指导；制备有机单晶薄膜晶体管阵列，基片覆盖度大于60%，平均迁移率高于5 cm^2/V.s；从水、氧、气压、温度和光电因素出发，系统研究单晶晶体管稳定性，为实用器件开发提供依据。

有机单晶薄膜场效应晶体管克服了传统非晶薄膜晶体管迁移率低的缺点，或将成为高性能有机柔软电路的基本构筑单元，也将为有机半导体中载流子传输等理论研究的完善和发展提供可靠的研究单元，因而有机单晶薄膜及晶体管的制备在新型电子器件开发和电子学理论发展方面有都有重要意义。.目前，有机单晶薄膜及晶体管制备研究还处于探索阶段，针对其制备方法不多，工艺重复性不高、成膜机理不完善等关键问题，本项目开发了由真空度控制溶剂挥发的挥发控制法制备晶态薄膜；还在此基础上，开发了一种易操作、工艺可控可重复的制备有机半导体晶态薄膜的新方法，即马兰格尼与咖啡环效应协同作用提拉法。该方法利用这两种溶剂的选择分别满足相对高沸点低表面张力和高表面张力低沸点的特点，在提拉成膜的过程中，促使溶液中的有机分子从成膜的起点向液体中移动，有效降低了溶剂自然挥发成膜引起的咖啡环效应，为均匀的单晶薄膜生长提供了条件。.利用该方法，以并五苯衍生物（Tips-Pentence）和并苯噻吩衍生物（C8-BTBT）为目标材料，研究了基片表面能、溶剂比例、溶液浓度、提拉速度等与成膜特性之间的关系，得到了有明显取向的晶态薄膜，基片覆盖率60-90%，并制备了薄膜晶体管器件，经过与理想晶体管特性对比校正，最高有效迁移率大于20 cm^2/V.s, 阈值电压低于 3 V, 开关电流比大于10^4。 .其次，我们还通过表面亲疏水处理，并经过提拉工艺的优化与选择，制备得到图案化的有序薄膜，迁移率也可以大于5 cm^2/V.s。.另外，我们还在研究有机半导体晶态薄膜及晶体管稳定性基础上，开发了有机薄膜晶体管在光敏、存储等方面的应用，合成了易于结晶成膜、具有窄波谱吸收的方酸类材料并研究了其在可见光通信方面的应用。.本项目研究期间，共发表SCI收录期刊论文16篇（其中3篇分别发表在 Advanced Materials，laser & Photonics Reviews 和 Nano Energy上），国际会议口头报告论文3篇，申请专利9项，其中4项获得授权。本项目较好地完成了计划，专利具有应用前景。此后我们还将在该领域继续深入研究，争取更多的成果。