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Working Principle of Organic Field Effect Transistor

Organic field effect transistors (OFETs) have attracted considerable attention due to their outstanding characteristics, such as wide source of materials, compatibility with flexible substrates, low temperature fabrication, suitability for mass production and low cost. It is widely used in all organic active display, large scale and ultra large scale integrated circuits, memory modules, sensors, organic lasers, complementary logic circuits and superconducting materials.

Organic field effect transistor working principle

Organic field effect transistors are composed of three electrodes: source drain, gate, organic semiconductor and gate insulation. According to the structure of devices, organic field effect transistors can be divided into four categories: bottom gate contact type, top gate contact type, neck gate bottom contact type and bottom gate I page contact type (Figure 1). The bottom gate and the top gate are divided according to the position of the gate, the bottom gate is deposited under the insulating layer of the gate, the top gate is deposited above the organic semiconductor and insulating layer, and the top contact and bottom contact are divided according to the position of the organic semiconductor and the source-drain electrode, and the top contact is that the organic semiconductor grows in the insulating layer of the gate and enters again. Deposition of row source and drain electrodes, while bottom contact is the base of organic semiconductors, which are source and drain electrodes and gate insulation layer. Different device structures will lead to different carrier injection modes and device performance. For example, in bottom-gate contact, carriers can be injected directly from the edge of the electrode into the conductive channel. In bottom-gate top contact, organic semiconductors separate the source-drain electrode from the conductive channel. Carriers injected from the conductive channel must be used. It is possible to increase the contact resistance and decrease the carrier injection efficiency by crossing the organic semiconductor layer. However, because the contact area between the electrode and the organic semiconductor is relatively large, the contact resistance becomes very small when the organic semiconductor layer is very thin. In addition, the performance of the device is better than that of the bottom contact because the term contact is deposited directly on the insulating layer by organic semiconductor materials and the quality of the film is better. However, considering the fabrication process, the top contact is that the source-drain electrodes are deposited on the organic semiconductor films, which may have some negative effects on the organic semiconductor, such as destroying the structure of the organic semiconductor. On the other hand, the size and integration of the top contact devices can not be smaller and higher than that of the bottom contact. Top contact is not suitable for large-scale production, which limits its practical application to a certain extent.

Organic field effect transistors are composed of three electrodes: source drain, gate, organic semiconductor and gate insulation. According to the structure of devices, organic field effect transistors can be divided into four categories: bottom gate contact type, top gate contact type, neck gate bottom contact type and bottom gate I page contact type (Figure 1). The bottom gate and the top gate are divided according to the position of the gate, the bottom gate is deposited under the insulating layer of the gate, the top gate is deposited above the organic semiconductor and insulating layer, and the top contact and bottom contact are divided according to the position of the organic semiconductor and the source-drain electrode, and the top contact is that the organic semiconductor grows in the insulating layer of the gate and enters again. Deposition of row source and drain electrodes, while bottom contact is the base of organic semiconductors, which are source and drain electrodes and gate insulation layer. Different device structures will lead to different carrier injection modes and device performance. For example, in bottom-gate contact, carriers can be injected directly from the edge of the electrode into the conductive channel. In bottom-gate top contact, organic semiconductors separate the source-drain electrode from the conductive channel. Carriers injected from the conductive channel must be used. It is possible to increase the contact resistance and decrease the carrier injection efficiency by crossing the organic semiconductor layer. However, because the contact area between the electrode and the organic semiconductor is relatively large, the contact resistance becomes very small when the organic semiconductor layer is very thin. In addition, the performance of the device is better than that of the bottom contact because the term contact is deposited directly on the insulating layer by organic semiconductor materials and the quality of the film is better. However, considering the fabrication process, the top contact is that the source-drain electrodes are deposited on the organic semiconductor films, which may have some negative effects on the organic semiconductor, such as destroying the structure of the organic semiconductor. On the other hand, the size and integration of the top contact devices can not be smaller and higher than that of the bottom contact. Top contact is not suitable for large-scale production, which limits its practical application to a certain extent.

Main performance indicators of OFET

The main requirements for organic semiconductor layers are as follows: first, stable electrochemical characteristics and good pi-conjugate system can facilitate carrier transport and obtain higher mobility; second, intrinsic conductivity must be low, in order to reduce leakage current of devices as much as possible, and thus improve the device. Switching ratio of components. In addition, OFET semiconductor materials should meet the following requirements: the lowest unoccupied molecular orbital (LUMO) or the highest occupied molecular orbital (HOMO) level of a single molecule is conducive to electron or hole injection; the solid crystal structure should provide sufficient molecular orbital overlap to ensure that the charge migrates between adjacent molecules without excessive energy barriers. Therefore, the main performance indicators of OFET are mobility, on-off current ratio and threshold voltage. The field mobility is the average drift velocity of charge carriers in a unit electric field, which reflects the mobility of holes or electrons in semiconductors under different electric fields. The on-off current ratio is defined as the leakage current ratio in the “on” and “off” states, which reflects the excellent switching performance of devices under a certain gate voltage. Inferior. In order to achieve commercial applications, the mobility of OFET is generally required to reach 0.O1cm2/(V.s), and the switching-on ratio is greater than 10. The threshold voltage should be as low as possible. Since the development of OFET, the voltage has dropped from tens or even hundreds of volts to 5V or even lower. The switching current ratio increases from 102 to 103 to 109, and the carrier mobility increases from 10-5 cm 2/(V.s) to 15.4 cm 2/(V.s).

Device performance is usually characterized by output characteristic curve and transfer characteristic curve.

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3 thoughts on “Working Principle of Organic Field Effect Transistor

  1. […] The relevant article about Organic Field Effect Transistors : Working Principle of Organic Field Effect Transistor […]

  2. […] Working Principle of Organic Field Effect Transistor […]

  3. Wow that was odd. I just wrote an very long comment but after I clicked submit my comment didn’t appear. Grrrr… well I’m not writing all that over again. Regardless, just wanted to say great blog!

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