By Michael D’Agati

Finding new materials and geometries for the creation of transistors has become a focal point in the field of electronics within the past decade. This transition from silicon-based materials is important towards keeping up with a prediction made by Intel co-founder Gordon Moore, which states that the number of transistors in a dense integrated circuit doubles every two years. In other words, every two years, the transistor either becomes physically smaller in size or more powerful in performance. New materials, such as poly (3,4-ethylenedioxythiophene) doped with polystyrenesulfonate (PEDOT: PSS) and new geometries, have shown promise for advancing the next generation of transistors.

This has led Dr. Fabio Cicoira and a team of scientists from Polytechnique Montreal, the University of Milan, and the University of Bologna to recently develop what they personally call a “transcap,” an organic field-effect transistor that integrates the properties of both a transistor and supercapacitor. The combination of both properties allows for a low-cost energy device that can be used in bioelectronics and other applications. In order to construct the device, the team used Mylar®, a flexible form of polyester resin, as a substrate, which gave the finished product its flexibility. Nanostructured carbon (nsC) films were deposited on the Mylar® as the gate electrodes, which control the flow of electrical current through the component. After many photolithography and patterning procedures, a gel electrolyte comprised of a mixture of PSSNa, D-sorbitol, glycerol, and deionized water was drop cast on top of the (PEDOT:PSS) channel and gate electrode and left to dry overnight.

In terms of transistor characteristics, the on/off ratio of the device was shown to be about 60, which demonstrates that nsC is a promising gate material. In terms of supercapacitor characteristics, the device demonstrated capacitances as much as 23 F/cm3 for 1 uA of current. As the current increased, the capacitance of the device decreased as expected.

The transcap, which serves as a hybrid between a transistor and supercapacitor, allows the development of an efficient and low-cost energy device that can be used in bioelectronics, as well as for flexible or stretchable electronics due to the Mylar® substrate. This is an innovative device that uses polymers and organic materials and possibly opens a new generation of electronic devices that incorporates multiple components into one efficient device.

References:

1. Z. Yi et al., Flexible conducting polymer transistors with supercapacitor function. Journal of Polymer Science (2016). doi: 10.1002/polb.24244.
2. Image retrieved from: https://upload.wikimedia.org/wikipedia/commons/2/27/TO-92%2C_BC548_%28front%2C_shaded%29.svg