Search

Organic electrochemical transistors (OECTs) show great potential in next-generation bioelectronics due to their high transconductance, low driving voltage, and biocompatibility. These advantages rely on efficient electrochemical doping/dedoping of the transistor channel consisting of organic mixed ionic–electronic conductors (OMIECs). Nevertheless, during device operation, hydration and electrolyte swelling lead to inferior cycling/operation stability of OECTs when compared with other conventional transistors. To enable further development and commercialization of OECTs, long-term stable operation is mandatory. Here, it is discovered that a slight variation in gate bias (VG) during operation would result in contrasting degradation in OECT performance with a conventional planar structure based on p-type p(g2T-T), which is the result of the alternating consumption of active OMIEC content due to the swelling effect during cycling. The introduction of the vertical architecture along with a crosslinking agent in the channel would largely decelerate/avoid such a process, which could yield an OECT with more than 250 000 full cycles (cycling duration of 10 000 s). Moreover, this strategy can be extended to another n-type OMIEC (Homo-gDPP). This work reveals a unique class of bioelectronics where their lifetime can be managed and controlled by device structure engineering, showing extensive potential in biomedical and bio-implantable functional devices. [ABSTRACT FROM AUTHOR]

Selenium incorporation is a widely used strategy for achieving high mobility semiconductors for a variety of organic optoelectronic devices, but it has received less attention in organic electrochemical transistors (OECTs). Herein, we developed two polythiophene derivatives (Pg2T-S and Pg2T-SVS) containing different selenophene loadings, as well as a selenophene-free polythiophene (Pg2T-T) as the control. The effects of selenium substitution/incorporation on the optical, electrical, electrochemical, and OECT performance of polythiophene-based organic mixed ionic–electronic conductors are systematically investigated. We discovered that introduction of selenium increases quinoidal character and crystallinity, which is beneficial for charge transport but makes ion penetration more challenging. In contrast, increasing selenium content increases the dipole moment and ion–polymer interaction, which is helpful for ion doping and volumetric capacitance but detrimental to charge transport. Therefore, appropriate selenium content should be evaluated to balance the trade-off between charge transfer and volumetric capacitance. As a result, Pg2T-S with moderate selenium loading achieves a high μC* of 332.7 F cm−1 V−1 s−1 with increased μ of 1.31 cm2 V−1 s−1 and maintains the C* value of 254 F cm−3. It also has a quick τon/τoff of 10.76 ms/5.90 ms and outstanding operational stability. Further introducing selenium boosts the dipole moment and ion–polymer interaction and therefore increased C*, but suppressed μ, resulting in inefficient μC*. We indicated that systematic balancing of the effects of selenium incorporation is necessary for the development of mixed ionic–electronic conductors for high-performance OECTs. [ABSTRACT FROM AUTHOR]