Small-molecule organic semiconductors have displayed remarkable electronic properties with a multitude of π-conjugated structures developed and fine-tuned over recent years to afford highly efficient hole- and electron-transporting materials. Already making a significant impact on organic electronic applications including organic field-effect transistors and solar cells, this class of materials is also now naturally being considered for the emerging field of organic bioelectronics. In efforts aimed at identifying and developing (semi)conducting materials for bioelectronic applications, particular attention has been placed on materials displaying mixed ionic and electronic conduction to interface efficiently with the inherently ionic biological world. Such mixed conductors are conveniently evaluated using an organic electrochemical transistor, which further presents itself as an ideal bioelectronic device for transducing biological signals into electrical signals. Here, we review recent literature relevant for the design of small-molecule mixed ionic and electronic conductors. We assess important classes of p- and n-type small-molecule semiconductors, consider structural modifications relevant for mixed conduction and for specific interactions with ionic species, and discuss the outlook of small-molecule semiconductors in the context of organic bioelectronics.

中文翻译：

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小分子半导体中的混合离子和电子传导

小分子有机半导体显示出显着的电子特性，近年来开发和微调了多种 π 共轭结构，以提供高效的空穴和电子传输材料。这类材料已经对包括有机场效应晶体管和太阳能电池在内的有机电子应用产生了重大影响，现在也自然地被考虑用于新兴的有机生物电子领域。在旨在识别和开发用于生物电子应用的（半）导电材料的努力中，特别关注显示混合离子和电子传导的材料，以有效地与固有的离子生物世界交互。使用有机电化学晶体管可以方便地评估这种混合导体，它进一步将自己作为一种理想的生物电子设备，用于将生物信号转换为电信号。在这里，我们回顾了与小分子混合离子和电子导体设计相关的最新文献。我们评估重要类别的 p 型和 n 型小分子半导体，考虑与混合传导和与离子物质的特定相互作用相关的结构修改，并讨论有机生物电子学背景下小分子半导体的前景。