Our paper “Sources and Mechanism of Degradation in p-Type Thiophene-Based Organic Electrochemical Transistors” was published in ACS Applied Electronic Materials.
Most work on OMIEC degradation focuses just on the polymer itself, and maybe the polymer in a particular electrolyte. While this is helpful, it doesn’t tell the whole story…what about device architecture and implementation? What about how you operate/bias the OECT?
If it’s pulsed in a diode-connected manner (G-D shorted), the degradation is much lower than when operated in a 3-terminal OECT or as an electrode (S-D shorted). It’s all about the combo of oxidative and reductive bias stress.
The reaction of dissolved oxygen at the buried Au/OMIEC interface of the drain electrode experiencing reductive potentials produces mobile reactive species that degrade the oxidized OMIEC in the device. This seems to be general across a number of thiophene p-type OMIECs.
This leads to design rules: we can avoid degradation by (1) removing oxygen (not practical for bioelectronics), (2) avoiding reductive potentials via the device biasing scheme, (3) replacing Au electrodes with a noncatalytic alternative, or (4) passivating Au electrodes with self-assembled monolayers.
This was a great team effort led by grad student Emily Schafer, with Ruiheng Wu, Dilara Meli, Josh Tropp and Bryan Paulsen, and, of course, with materials from Iain McCulloch and team.