Field Effect Transistor (FET) is an active device that uses an electric field to control the conductivity of solid materials. Due to its small size, light weight, low power consumption, good thermal stability, no secondary breakdown, and wide safe working area, it has become one of the important components in the microelectronics industry. Organic transistor (OFET) refers to a device prepared by using organic semiconductors as the active material of FET. OFET is similar in structure to a capacitor. The source and drain electrodes and the conductive channel of the organic semiconductor film are equivalent to one plate, and the grid is equivalent to another plate. When a negative voltage is applied between the gate and the source, positively charged holes will be induced in the semiconductor layer near the insulating layer, and negatively charged electrons will accumulate at the gate. At this time, adding a negative voltage between the source and drain electrodes will generate a current between the source and drain electrodes. The intensity of the electric field in the insulating layer can be adjusted by adjusting the voltage, and the density of the induced charge is different with the intensity of the electric field. Therefore, the width of the conductive path between the source and the drain is different, and the current between the source and the drain also changes. OFET materials have the advantages of a wide range of material sources, low working voltage, compatibility with flexible substrates, suitable for low-temperature processing, suitable for mass production, low cost, and solution processing into films, etc., and have been widely used in the preparation of new materials and device processes etc.
Figure 1. Typical organic transistor (OFET) materials structure
- Organic memory circuit components: Since OFET as a storage device has the advantages of non-destructive reading and supplementing the compatibility of metal oxide semiconductors, it is used to prepare permanent organic non-volatile memory devices (ONVM). It is a polymer dielectric through the storage of charges in an organic polymer dielectric that can store charges, so as to achieve the storage effect.
- Organic flat panel display technology: The advantages of organic thin film transistors (OTFF), such as flexibility, high speed, and excellent photoelectric performance, are also widely used in the field of organic flat panel display driving. The use of transistor-driven display panels can greatly reduce the complexity of the device.
- Preparation of organic superconducting materials: After a voltage is applied between the gate and source of the OFET, a large amount of charge is accumulated in the organic semiconductor film and the insulating layer. Adjusting the size of the gate voltage can control the charge density, and by increasing the charge carrier density, the superconducting characteristics of the field effect transistor can be guided to realize the transformation from an insulator to a superconductor, and an organic superconducting material can be prepared.
- Gas sensor: OFET transistors made of organic thin films can be used as gas sensors, and their biggest advantage is that they are very thin. The phthalocyanine film made by vacuum evaporation can be used as NO2 sensor, showing a very low detection limit (<50 ppb), and has a very good response sensitivity. Using gallium hydroxide mixed with a cellulose-trimethylsilyl derivative, thin films of different forms are made by a spin coating method, which has a sensitive detection effect on ozone and nitrogen.
- Sandeep G. Surya,Harshil N. Raval,Rafiq Ahmad,Prashant Sonar,Khaled N. Salama,V.Ramgopal Rao. Organic field effect transistors (OFETs) in environmental sensing and health monitoring: A review [J]. Trends Anal. Chem., 2019, 11, 27-36.