Organic Electrochemical Transistors Based on Room Temperature Ionic Liquids: Performance and Stability

• Published in: Physica status solidi. A, Applications and materials science Applications and materials science, 2018-12, Vol.215 (24), p.n/a
• Main Authors: Kaphle, Vikash, Liu, Shiyi, Keum, Chang‐Min, Lüssem, Björn
• Format: Article
• Language: English
• Subjects: Electrolytes; gate stress bias; Hysteresis; Ionic liquids; Ions; organic electrochemical transistor; PEDOT:PSS; Recording; Room temperature; Semiconductor devices; Solvents; Stability; Switching; Transistors
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.201800631

Organic electrochemical transistors (OECTs) are becoming a key device in the field of organic bioelectronics. For many applications of OECTs, in particular for enzymatic sensing, a complex mixture of room temperature ionic liquids (RTILs) combined with other electrolytes is used as a gate electrolyte, making the interpretation of experimental trends challenging. Here, the switching mechanism of OECTs using such RTILs is studied. It shows that ions smaller in size than the ions contained in the RTIL (e.g., Na+) have to be added to the ionic liquid to ensure switching of the OECTs. Furthermore, it is shown that OECTs based on RTILs exhibit noticeable gate‐bias stress effects and a hysteresis in the electrical transfer characteristics. A model based on incomplete charging/discharging of the effective gate capacitance during operation of the OECT and a dispersion in the ion mobilities is proposed to explain these instabilities, and thus it shows that the hysteresis can be minimized by optimizing the geometry of the device. Overall, a better understanding of the underlying mechanisms of switching and stability of OECTs based on RTILs is the first step toward various applications such as lactate acid sensors and neurotransmitter recording. Organic electrochemical transistors (OECTs) are a key device in the field of organic bioelectronics. The switching mechanism and stability of OECTs based on room‐temperature ionic liquids is studied. A model is proposed to discuss gate‐bias stress effects and it shows that the shift in pinch‐off voltage can be reduced by geometrical optimization of the gate electrode and the electrolyte.