This journal is © The Royal Society of Chemistry and the Chinese Chemical Society 2020 Mater. Chem. Front., 2020, 4, 3505--3520 | 3505 Cite this: Mater. Chem. Front., 2020, 4, 3505 Structured and functionalized organic semiconductors for chemical and biological sensors based on organic field effect transistors† Yujing Wang, Qi Gong and Qian Miao * One of the most promising applications of organic field-effect transistors (OFETs) is chemical and biological sensing. In order to achieve highly sensitive and selective detection of a broad array of analytes, the organic semiconductor layer in an OFET is tailored with rationally designed physical structures and chemical functionalities. This article reviews representative studies on structured and functionalized organic semiconductors after a brief introduction to OFET-based chemical and biological sensors. Finally, we reach conclusions on the achievements and challenges in this research field and provide an outlook for the development in the near future. Introduction This review aims to provide an overview of strategies to tailor organic semiconductors with rationally designed physical structures and chemical functionalities to develop chemical and biological sensors based on organic field effect transistors (OFETs). An OFET typically consists of a thin film of organic semiconductors, three electrodes (gate, drain and source) and a dielectric layer between the semiconductor and the gate electrode as shown in Fig. 1a. An OFET essentially acts as an on/off switch, where the electrical current flowing between the drain and source electrodes (I DS ) is controlled by the voltage between the gate and source electrodes (V GS ) under an imposed bias between the drain and source electrodes (V DS ). The velocity of charge carriers (holes or electrons for p- or n-type organic semiconductors, respectively) in OFETs is quantified by the field effect mobility, which is the most important parameter to characterize the performance of OFETs. OFETs are promising platforms for various types of sensors 1–4 with a unique combi- nation of advantages. First, the electronic input and output characteristics of OFETs can be modulated by a variety of physical and chemical stimuli through different mechanisms. For example, light or heat can greatly affect the conductivity of organic semiconductors by altering the density and mobility of charge carriers, and mechanical work can influence the gate voltage applied to the conduction channel. Second, OFET-based sensors can be fabricated on flexible substrates over large area at low cost because organic semiconductors, unlike Department of Chemistry, the Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China. E-mail: miaoqian@cuhk.edu.hk † We dedicate this paper to Prof. Fred Wudl on the occasion of his 80th birthday. Yujing Wang Yujing Wang was born in China in 1995. She received her Bachelor’s degree in chemistry and materials science from the University of Science and Technology of China (USTC) in 2017. She is currently a PhD candidate in Prof. Qian Miao’s group at the Chinese University of Hong Kong (CUHK). Her research interests focus on the synthesis of functionalized poly- cyclic aromatic molecules and their applications in electronic devices. Qi Gong Qi Gong was born in China in 1997. She received her BS degree in chemistry from the University of Science and Technology of China (USTC) in 2019. Now she is a PhD student in the research group of Prof. Qian Miao in the Chemistry Department of the Chinese University of Hong Kong (CUHK). Her research focuses on gas sensors based on organic field effect transistors. Received 31st March 2020, Accepted 30th May 2020 DOI: 10.1039/d0qm00202j rsc.li/frontiers-materials MATERIALS CHEMISTRY FRONTIERS REVIEW Published on 02 June 2020. Downloaded on 2/19/2022 11:44:18 AM. View Article Online View Journal | View Issue