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Organic light-emitting electrochemical cells (LEC) are promising for lighting applications but in many cases these devices suffer from unbalanced electrochemical doping, which cause instability and degradation of the cells. A predominant p-doping over n-doping causes an off-centered emissive p–n junction, which leads to poor power-conversion efficiency. Here, we report a half-gate LEC transistor (HG-LECT), in which an ion-conductive gate made from poly(3,4-ethylenedioxythiophene)-poly-(styrenesulfonate) is employed to combat this instability problem. The gate material, covering half of the channel, is used to enhance the n-doping process in this part by employing an appropriate operation protocol. We demonstrate a centered light emission zone, closely following the geometry of the gate configuration. The HG-LECT with centered emission profile is shown to be more efficient than the corresponding LEC without the gate electrode, and its n-doping level is measured to be 15%. [ABSTRACT FROM AUTHOR]

Low-voltage-operating organic electrochemical light-emitting cells (LECs) and transistors (OECTs) can be realized in robust device architectures, thus enabling easy manufacturing of light sources using printing tools. In an LEC, the p-n junction, located within the organic semiconductor channel, constitutes the active light-emitting element. It is established and fixated through electrochemical p- and n-doping, which are governed by charge injection from the anode and cathode, respectively. In an OECT, the electrochemical doping level along the organic semiconducting channel is controlled via the gate electrode. Here we report the merger of these two devices: the light-emitting electrochemical transistor, in which the location of the emitting p-n junction and the current level between the anode and cathode are modulated via a gate electrode. Light emission occurs at 4 V, and the emission zone can be repeatedly moved back and forth within an interelectrode gap of 500 μm by application of a 4 V gate bias. In transistor operation, the estimated on/off ratio ranges from 10 to 100 with a gate threshold voltage of -2.3 V and transconductance value between 1.4 and 3 μS. This device structure opens for new experiments tunable light sources and LECs with added electronic functionality. [ABSTRACT FROM AUTHOR]

The nature of mass transport in plants has recently inspired the development of low-cost and sustainable wood-based electronics. Herein, we report a wood electrochemical transistor (WECT) where all three electrodes are fully made of conductive wood (CW). The CW is prepared using a two-step strategy of wood delignification followed by wood amalgamation with a mixed electron-ion conducting polymer, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS). The modified wood has an electrical conductivity of up to 69 Sm-1 induced by the formation of PEDOT:PSS microstructures inside the wood 3D scaffold. CW is then used to fabricate the WECT, which is capable of modulating an electrical current in a porous and thick transistor channel (1 mm) with an on/off ratio of 50. The device shows a good response to gate voltage modulation and exhibits dynamic switching properties similar to those of an organic electrochemical transistor. This wood-based device and the proposed working principle demonstrate the possibility to incorporate active electronic functionality into the wood, suggesting different types of bio-based electronic devices. [ABSTRACT FROM AUTHOR]

Organic electronic circuits based on organic electrochemical transistors (OECTs) are attracting great attention due to their printability, flexibility, and low voltage operation. Inverters are the building blocks of digital logic circuits (e.g., NAND gates) and analog circuits (e.g., amplifiers). However, utilizing OECTs in electronic logic circuits is challenging due to the resulting low voltage gain and low output voltage levels. Hence, inverters capable of operating at relatively low supply voltages, yet offering high voltage gain and larger output voltage windows than the respective input voltage window are desired. Herein, inverters realized from poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate‐based OECTs are designed and explored, resulting in logic inverters exhibiting high voltage gains, enlarged output voltage windows, and tunable switching points. The inverter designs are based on multiple screen‐printed OECTs and a resistor ladder, where one OECT is the driving transistor while one or two additional OECTs are used as variable resistors in the resistor ladder. The inverters' performances are investigated in terms of voltage gain, output voltage levels, and switching point. Inverters, operating at +/−2.5 V supply voltage and an input voltage window of 1 V, that can achieve an output voltage window with ∼110% increment and a voltage gain up to 42 are demonstrated. [ABSTRACT FROM AUTHOR]

Low‐voltage operating organic electronic circuits with long‐term stability characteristics are receiving increasing attention because of the growing demands for power efficient electronics in Internet of Things applications. To realize such circuits, inverters, the fundamental constituents of many circuits, with stable transfer characteristics should be designed to provide low‐power consumption. Here, a rational inverter design, based on fully screen printed p‐type organic electrochemical transistors with a channel size of 150 × 80 µm2, is explored for driving conditions with input voltage levels that differs of about 1 V. Further, three different inverter circuits are explored, including resistor ladders with resistor values ranging from tens of kΩ to a few MΩ. The performance of single inverters, 3‐stage cascaded inverters and 3‐stage ring oscillators are characterized with respect to output voltage levels, propagation delay, static power consumption, voltage gain, and operational frequency window. Depending on the application, the key performance parameters of the inverter can be optimized by the specific combination of the input voltage levels and the resistor ladder values. A few of the inverters are in fact fully functional up to 30 Hz, even when using input voltage levels as low as (0 V, 1 V). [ABSTRACT FROM AUTHOR]