Mixed Ionic and Electronic Conduction in Small-Molecule Semiconductors

Abstract

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.

Highly Efficient Mixed Conduction in N‐type Fused Small Molecule Semiconductors

“…[29,30] Small molecule semiconductors have been reported to display high charge carrier mobility exceeding 10 cm 2 V −1 s −1 in OFETs, which can be attributed to its opportune crystallinity, associated with several advantages of high purity with irrefutable structure, facile synthesis, industrial scale-up, and no batch-to-batch variations to lead straightforward structureproperty relations in contrast to polymeric semiconductors. [15,31] Therefore, small molecule semiconductors are expected to be potential next-generation high-performance OECT materials for real-world application. However, small molecule semiconductors OECT materials, particularly n-type, have not gained much attention and their figures of merit performance parameters lag much behind their conjugated polymers counterparts.…”

Structures, Properties, and Device Applications for [1]Benzothieno[3,2‐b]Benzothiophene Derivatives

“…[1][2][3] Organic small molecular semiconducting materials have many advantages as compared with conjugated polymer semiconductors. [4,5] The physical and chemical properties of organic small molecules can be effectively and easily controlled by adjusting functional groups and molecular structures. Furthermore, the stable molecular structures and intimate interaction between molecules are favorable for the formation of regularly ordered solid packing.…”

Hybrid Organic-Inorganic Materials and Interfaces With Mixed Ionic-Electronic Transport Properties: Advances in Experimental and Theoretical Approaches

“…There are a lot of recent examples of h OI materials with promising mixed ionic-electronic transport properties in different applications such as lithium and sodium-ion battery electrode ( Sengodu and Deshmukh, 2015 ) and bio-electronic materials ( Kousseff et al, 2022 ; Kukhta et al, 2022 ). There are also recent reviews on the most relevant and popular techniques that can be useful to characterize experimentally the mixed ionic-electronic transport in h OI materials ( Romero et al, 2020 ; Wu et al, 2022 ).…”