Interplay between Electrolyte-Gated Organic Field-Effect Transistors and Surfactants: A Surface Aggregation Tool and Protecting Semiconducting Layer

Abstract

Molecular surfactants, which are based on a water-insoluble tail and a water-soluble head, are widely employed in many areas, such as surface coatings or for drug delivery, thanks to their capability to form micelles in solution or supramolecular structures at the solid/liquid interface. Electrolyte-gated organic field-effect transistors (EGOFETs) are highly sensitive to changes occurring at their electrolyte/gate electrode and electrolyte/organic semiconductor interfaces, and hence, they have been much explored in biosensing due to their inherent amplification properties. Here, we demonstrate that the EGOFETs and surfactants can provide mutual benefits to each other. EGOFETs can be a simple and complementary tool to study the aggregation behavior of cationic and anionic surfactants at low concentrations on a polarized metal surface. In this way, we have monitored the monolayer formation of cationic and anionic surfactants at the water/electrode interface with p - type and n - type devices, respectively. On the other hand, the operational stability of EGOFETs has been dramatically enhanced, thanks to the formation of a protective layer on top of the organic semiconductor by exposing it to a high concentration of a surfactant solution (above the critical micelle concentration). Stable performances were achieved for more than 10 and 2 h of continuous operation for p - type and n-type devices, respectively. Accordingly, this work points not only that EGOFETs can be applied to a wider range of applications beyond biosensing but also that these devices can effectively improve their long-term stability by simply treating them with a suitable surfactant.

Investigation and Modeling of the Electrical Bias Stress in Electrolyte‐Gated Organic Transistors

“…This may be ascribed to the intercalation of water molecules in the polymer film after prolonged exposure to the aqueous electrolyte, with a consequent decrease of the hole mobility. [31,32] For P3CPT, the analysis confirmed the detrimental effect of the EBS over the polymer behavior. In particular, the absolute value of the V T continuously increased because of the bias stress, which consequently made the transistor always more difficult to switch-on for the same applied gate voltage (Figure 8c).…”

“…This may be ascribed to the intercalation of water molecules in the polymer film after prolonged exposure to the aqueous electrolyte, with a consequent decrease of the hole mobility. [ 31,32 ]…”

Robust Microfluidic Integrated Electrolyte‐Gated Organic Field‐Effect Transistor Sensors for Rapid, In Situ and Label‐Free Monitoring of DNA Hybridization

“…This trend, an increase of I DS over bias stressing, has been observed in an EGOFET in which the OSC was protected by SAM of cationic/anionic molecules. [ 29 ] Such bias stress instability could originate from charge detrapping from the OSC and polarisation or ion drift in the EDL. It should be emphasized that the current retention during 1h continuous operation observed in the developed device is significantly higher than that of previously reported EGOFETs (≈96% vs 60% to ≈90%) despite the flow of the electrolyte and the higher gate bias ( V GS = –1.2 V).…”

“…It should be emphasized that the current retention during 1h continuous operation observed in the developed device is significantly higher than that of previously reported EGOFETs (≈96% vs 60% to ≈90%) despite the flow of the electrolyte and the higher gate bias (V GS = -1.2 V). [30,29] The improved operational stability may come from the more ordered morphology and the interdigitation of the alkyl side chains reducing water diffusion and ion doping. [18] Similarly, the initial I GS rapidly decreased to reach 96% of its minimum value after 100 s (lower panel of the inset of Figure 3a).…”

“…This is relatively stable than previously reported results on EGOFET stability over bias stressing (≈13% vs >15% up to 25%). [30,29,16] For the other figures of merit, it was found that they also drift by ≈15% when cycled continuously for an hour of operation. V th and μ × C i changed by ≈14% and ≈10%, respectively (middle and right panel of Figure 3c).…”