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Printed subthreshold organic transistors operating at high gain and ultralow power

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Science  15 Feb 2019:
Vol. 363, Issue 6428, pp. 719-723
DOI: 10.1126/science.aav7057
  • Fig. 1 Device structure and electrical characteristics.

    (A) Schematic cross section of the SB-OTFT. PS, polystyrene; PVC, polyvinyl cinnamate; PEN, polyethylene naphthalate. (B and C) Measured transfer characteristics (ID versus VGS) of a typical device (B) on a linear scale, indicating the threshold voltage (VT), and (C) on a log scale, indicating the subthreshold slope (SS). dec, decade. (D and E) Statistical distributions of (D) SS and (E) VT for 50 devices. The dashed lines indicate normal distributions. (F) Measured output characteristics (ID versus VDS) indicating the output resistance (ro) of devices with different channel lengths (L) and showing a full overlap of the characteristics. The inset shows ro versus L.

  • Fig. 2 Static parameters.

    (A) DOS for a typical device, indicating four different regimes: deep states, delocalized-tail (DT) states, localized-tail (LT) states, and extended (E) states. The slopes in the DT and LT regimes indicate the characteristic energies (kBTDT and kBTLT, respectively). gtot, density of states. (B) Effective Schottky barrier heights (Φeff) as a function of VGS, indicating the gate modulation factor (ζ0) for the Φeff lowering. (Inset) Schematic energy band diagram showing variation in effective Φeff and different charge-carrier injection processes. TFE, thermionic field emission; TE, thermionic emission. (C) Experimental values for gm and ro as a function of VGS. Ω, ohms. (D) Measured intrinsic gain (Ai) as a function of VGS. Si-MOSFET, Si metal oxide semiconductor field-effect transistor. (E) Experimental values of transconductance efficiency (gm/ID) as a function of VGS, reaching the theoretical thermionic limit of 38.7 S/A.

  • Fig. 3 Stability and reliability.

    (A) Measured transfer characteristics for a TFT in storage under ambient conditions for the times indicated and (B) change in absolute threshold voltage (ΔVT) and change in relative transconductance efficiency [Δ(gm/ID)] as a function of time. (C) Measured transfer characteristics under negative bias stress (VGS = VDS = −3 V) for the stress time indicated and (D) ΔVT and Δ(gm/ID) as a function of stress time. (E) Measured transfer characteristics under light exposure and (F) photocurrent (Iphoto in amperes per micrometer) and ΔVT for different wavelengths (400 to 800 nm). (G) Measured SB-OTFT current noise under different direct current biases (IDC). (H) SNRs in the near-threshold and subthreshold regimes and input-referred voltage noise density at 100 Hz. a-Si, amorphous silicon.

  • Fig. 4 Amplifier characteristics and demonstration of EOG detection.

    (A) Schematic circuit diagram of a common-source amplifier. VDD, supply voltage; IB, bias current. (B) Measured output voltage (Vout) and gain (AV) as a function of input voltage (Vin). (C) Measured operating current (IDD) and power (Pout) as functions of Vin. (D) Resolution of electrophysiological signal detection as a function of gain. (E) Gain-bandwidth product as a function of VGS in the subthreshold regime. (F) Operating principle and circuit configuration for EOG amplification with the amplifier. (G) EOG signal obtained before and after amplification.

Supplementary Materials

  • Printed subthreshold organic transistors operating at high gain and ultralow power

    Chen Jiang, Hyung Woo Choi, Xiang Cheng, Hanbin Ma, David Hasko, Arokia Nathan

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods
    • Supplementary Text
    • Figs. S1 to S12
    • Tables S1 and S2
    • Captions for Movie S1
    • References

    Images, Video, and Other Media

    Movie S1
    Electro-oculogram (EOG) monitoring by fully-printed SB-OTFT amplifier. The amplifier was connected to the electrodes around the human eye as in Fig. 4F. The EOG signal was acquired and magnified by the amplifier. When the eyeball moved up, the output voltage increased, and vice versa.

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