Balanced Sensitivity and Detection Range in Ion-Selective OECTs by Gate Bias Modulation
Ion-selective organic electrochemical transistors (IS-OECTs) are promising for biofluid ion detection due to biocompatibility, low operating voltage, and signal amplification. However, their performance is constrained by the nonlinear relationship between effective ion-selective membrane (ISM) potential and gate bias, which causes unstable and degraded current sensitivity (SI) over wide concentration ranges. This work introduces gate bias modulation to maintain high transconductance (gm) across all ion concentration subranges, simultaneously achieving wide detection range and ultrahigh sensitivity. By modulating gate bias from 0.7 to 0.95 V, Ca2+ and NH4+-IS-OECTs based on small-footprint (640 μm2) n-type vertical OECTs (vOECTs) exhibit approximately 3 mA/dec over a wide ionic range of 10−5 to 10−1 M, the highest SI reported for Ca2+ and NH4+ ion-sensitive transistors. This approach provides a general strategy for ultrahigh sensitivity and wide detection range IS-OECTs, extendable to other transistor-based biomolecule and ion sensors, offering insights for advancing high-performance bioelectronics.