在过去的二十年里,有机场效应晶体管(OFET)已经引起了科学界和工业界越来越多的关注。OFET的性能可以基于三个因素进行评估:电荷传输迁移率(μ),阈值电压(Vth),和电流开/关比(离子/关)。为了增强μ,许多研究集中在优化半导体层内的电荷传输。这些努力包括:(I)扩展π-共轭,增强分子平面性,和优化供体-受体结构以改善单个分子内的电荷传输;和(ii)促进强聚集,实现有序的结构,并减少分子间的距离以增强分子间的电荷传输。为了获得高的电荷传输迁移率,从电极到半导体层中的电荷注入也很重要。由于合适的前沿分子轨道水平可以与电极的功函数对齐,进而在界面处形成欧姆接触。OFET分为p型(空穴传输),n型(电子传输),和双极性类型(空穴和电子传输)基于它们的电荷传输特性。截至目前,大多数报道的共轭材料属于p型半导体类别,n型或双极性共轭材料的研究明显滞后。这篇综述介绍了用于增强电荷载流子迁移率的分子设计概念,在半导体层内和电荷注入方面进行寻址。此外,总结了设计或转换半导体类型的过程。最后,这篇综述讨论了进化和挑战的潜在趋势,并提供了展望;最终目标是概述设计高性能有机半导体的理论框架,可以促进OFET应用的发展。
In the last two decades, organic field-effect transistors (
OFETs) have garnered increasing attention from the scientific and industrial communities. The performance of
OFETs can be evaluated based on three factors: the charge transport mobility (μ), threshold voltage (Vth), and current on/off ratio (Ion/off). To enhance μ, numerous studies have concentrated on optimizing charge transport within the semiconductor layer. These efforts include: (i) extending π-conjugation, enhancing molecular planarity, and optimizing donor-acceptor structures to improve charge transport within individual molecules; and (ii) promoting strong aggregation, achieving well-ordered structures, and reducing molecular distances to enhance charge transport between molecules. In order to obtain a high charge transport mobility, the charge injection from the electrodes into the semiconductor layer is also important. Since a suitable frontier molecular orbitals\' level could align with the work function of the electrodes, in turn forming an Ohmic contact at the interface.
OFETs are classified into p-type (hole transport), n-type (electron transport), and ambipolar-type (both hole and electron transport) based on their charge transport characteristics. As of now, the majority of reported conjugated materials are of the p-type semiconductor category, with research on n-type or ambipolar conjugated materials lagging significantly behind. This
review introduces the molecular design concept for enhancing charge carrier mobility, addressing both within the semiconductor layer and charge injection aspects. Additionally, the process of designing or converting the semiconductor type is summarized. Lastly, this
review discusses potential trends in evolution and challenges and provides an outlook; the ultimate objective is to outline a theoretical framework for designing high-performance organic semiconductors that can advance the development of OFET applications.