直写单晶制备高性能有机场效应晶体管

有机场效应晶体管的溶液法制备工艺对于柔性电子产业化具有重要意义。使用单晶作为有机场效应晶体管的活性层是提高其性能的关键。然而目前制备有机半导体单晶的工艺存在晶体取向性差、难以大面积生产等问题，阻碍了有机场效应晶体管的进一步应用。

为了制备大面积有机半导体单晶，本文基于弯月面引导涂布法，提出一种直写单晶制备有机场效应晶体管的新工艺。基于芯吸理论和狭缝供液理论，设计了一种柔性直写笔。该装置可以直接接触基底，形成稳定可控的弯月面。可拓展成多路复用和刷子形态，实现单路、多路、大面积单晶制备。既能满足精细图案化需求，又能实现多路并行及大面积刷涂，提高生产效率。

弯月面及其稳定性是决定晶体形貌长程有序性和取向性的关键。本文分析弯月面内流动规律和弯月面外的蒸发沉积规律。建立固体薄膜的蒸发沉积的数学模型。基于多物理场仿真分析软件STAR-CCM+建立本工艺的数值模型，验证弯月面流动规律。

为了解蒸发结晶的动态过程，建立原位拍摄系统，实时捕捉涂布过程，分析流体流动对晶体形貌的影响。关注“弯月面-前驱膜-接触线-晶体”这一重要结构，分析前驱膜失稳和无序晶体的对应关系。通过涂布速度和基板温度的正交实验探索最优工艺参数，为制作器件提供指导。

制备有机场效应晶体管器件，最高迁移率为0.60 cm²V^-1s^-1。分析迁移率与晶体取向角的关系，讨论使用多路复用和大面积刷涂形态时器件迁移率一致性，论证本工艺提高生产效率的能力。本文提出的柔性直写装置，为有机半导体单晶及晶体管器件的大面积、低成本、高产量制备提供理论、数值和实验基础。

The solution processing of organic field-effect transistors is significant for the industrialization of flexible electronics. Utilizing single crystals as the active layer of OFETs is essential to improve their performance. However, the existing methods for preparing organic semiconductor single crystals encounters obstacles such as poor crystal orientation and difficulties in achieving large-scale production, thereby impeding the further development of OFETs.

To prepare organic semiconductor single crystals on a large scale, this thesis proposes a novel process for direct-writing single crystals based on meniscus-guided coating. A flexible direct-writing pen is designed based on the Lucas-Washburn Law and slot’s liquid supply theory. The direct-writing pen enables direct contact the substrate, facilitating the formation of a stable and controllable meniscus. In addition, the direct-writing pen can be extended to multiplexed and brush-like configurations to enable large-scale fabrication of single crystals.

The meniscus and its stability play a pivotal role in determining the long-range ordered crystal with high orientation. The flow field inside the meniscus and the deposition pattern outside the meniscus was analyzed. Leveraging the multi-physics simulation software STAR-CCM+, a numerical model is established to visualize the flow field of the meniscus.

In order to comprehend the dynamic crystallization process, an in-situ observation system is implemented to capture real-time crystallization. This allows for an analysis of the influence of fluid flow on crystal morphology. The important structure of "meniscus--precursor--contact line--crystal" is focused on, and the corresponding relationship between the instability of the precursor and the disorder of the crystal is analyzed. Furthermore, an orthogonal experiment involving coating speed and substrate temperature is conducted to explore the optimal process parameters, thereby providing guidance for device fabrication.

OFET devices are fabricated and the highest mobility is 0.60 cm²V^-1s^-1. The relationship between mobility and crystal orientation angle is analyzed, and the consistency of device mobilities based on multiplexed configuration is discussed. This demonstrates the capability of the proposed approach to increase throughput while maintaining high consistency. The flexible direct-writing apparatus presented in this thesis establishes a theoretical, numerical, and experimental foundation for the low-cost, large-scale, and high throughput of organic semiconductor single crystals and OFET devices.

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