Deyu Tu

A Static Model for Electrolyte-Gated Organic Field-Effect Transistors

We present a dc model to simulate the static performance of electrolyte-gated organic field-effect transistors. The channel current is expressed as charge drift transport under electric field. The charges accumulated in the channel are considered being contributed from voltage-dependent electric-double-layer capacitance. The voltage-dependent contact effect and short-channel effect are also taken into account in this model. A straightforward and efficient methodology is presented to extract the model parameters. The versatility of this model is discussed as well. The model is verified by the good agreement between simulation and experimental data.

Electrochromic Electrochemical Transistors Gated With Polyelectrolyte-Decorated Amyloid Fibrils

This paper presents the use of polyelectrolyte-decorated amyloid fibrils as gate electrolyte in electrochromic electrochemical transistors. Conducting polymer alkoxysulfonate poly(3,4-ethylenedioxythiophene) (PEDOT-S) and luminescent conjugate polymer poly(thiophene acetic acid) (PTAA) are utilized to decorate insulin amyloid fibrils for gating lateral poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) electrochemical transistors. In this comparative work, four gate electrolytes are explored, including the polyelectrolytes and their amyloid-fibril complexes. The discrimination of transistor behaviors with different gate electrolytes is understood in terms of an electrochemical mechanism. The combination of luminescent polymers, biomolecules and electrochromic transistors enables multi functions in a single device, for example, the color modulation in monochrome electrochromic display, as well as biological sensing/labeling.

Transient analysis of electrolyte-gated organic field-effect transistors

A terminal charge and capacitance model is developed for transient behavior simulation of electrolyte-gated organic field effect transistors (EGOFETs). Based on the Ward-Dutton partition scheme, the charge and capacitance model is derived from our drain current model reported previously. The transient drain current is expressed as the sum of the initial drain current and the charging current, which is written as the product of the partial differential of the terminal charges with respect to the terminal voltages and the differential of the terminal voltages upon time. The validity for this model is verified by experimental measurements.

A Silicon-Organic Hybrid Voltage Equalizer for Supercapacitor Balancing

Cell voltage equalizers are an important part in electric energy storage systems comprising series-connected cells, for example, supercapacitors. Hybrid electronics with silicon chips and printed devices enables electronic systems with moderate performance and low cost. This paper presents a silicon-organic hybrid voltage equalizer to balance and protect series-connected supercapacitor cells during charging. Printed organic electrochemical transistors with conducting polymer poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) are utilized to bypass excess current when the supercapacitor cells are fully charged to desired voltages. In this study, low-cost silicon microcontrollers (ATtiny85) are programmed to sense voltages across the supercapacitor cells and control the organic electrochemical transistors to bypass charging current when the voltages exceed 1 V. Experimental results show that the hybrid equalizer with the organic electrochemical transistors works in dual-mode, switched-transistor mode or constant-resistor mode, depending on the charging current applied (0.3–100 mA). With the voltage equalizer, capacitors are charged equally regardless of their capacitances. This work demonstrates a low-cost hybrid solution for supercapacitor balancing modules at large-scale packs.

The applications of OECTs in supercapacitor balancing circuits

In this paper, we investigate using OECTs in differential amplifiers and cell voltage equalizers for supercapacitor balancing circuits. The differential amplifier based on OECTs can sense voltage difference and the voltage equalizer consisting of a microcontroller and OECTs can be used to charge supercapacitors to desired voltages.

Modeling of Drain Current Mismatch in Organic Thin-Film Transistors

In this paper, we present a consistent model to analyze the drain current mismatch of organic thin-film transistors. The model takes charge fluctuations and edge effects into account, to predict the fluctuations of drain currents. A Poisson distribution for the number of charge carriers is assumed to represent the random distribution of charge carriers in the channel. The edge effects due to geometric variations in fabrication processes are interpreted in terms of the fluctuations of channel length and width. The simulation results are corroborated by experimental results taken from over 80 organic transistors on a flexible plastic substrate.

Parameter extraction for electrolyte-gated organic field effect transistor modeling

We present a methodology to extract parameters for an electrolyte-gated organic field effect transistor DC model. The model is based on charge drift/diffusion transport under electric field and covers all regimes. Voltage dependent capacitance, mobility, contact resistance and threshold voltage shift are taken into account in this model. The feature parameters in the model are simply extracted from the transfer or output characteristics of electrolyte-gated organic field effect transistors. The extracted parameters are verified by good agreements between experimental and simulated results.