Correctly characterizing the properties of organic semiconductors is the key to understanding their intrinsic mechanisms of action and facilitating their practical applications. For organic semiconductors, mobility is one of the most critical performance parameters to judge their performance. The mobility of organic semiconductors is usually calculated by preparing organic field effect transistors and analyzing the transfer characteristic curve of the device using the Shockley formula. This formula is derived based on an ideal hypothetical model, so it is usually only applicable to ideal linear transfer characteristics. However, in organic semiconductors, organic molecules are bound by weak intermolecular interactions, and the ordered stacking of organic molecules is easily damaged by external factors during the actual device fabrication process, and various defects are inevitably generated, making the device Deviation from ideal field effect transistor behavior. Applying Shockley's formula directly to non-ideal devices can lead to incorrect estimates of mobility. Therefore, the construction of field effect transistors with ideal operating characteristics is of great significance to correctly evaluate the performance of organic semiconductors and to promote their practical applications.

Organic field effect transistors often exhibit non-ideal behavior in air due to the presence of active components (water and oxygen) in the air atmosphere. Existing ideality studies mainly focus on the role of water and oxygen adsorbed on the interface of the insulating layer, which are believed to negatively affect the ideal behavior of the device through interfacial charge trapping. However, little attention has been paid to the direct effects of water and oxygen on the organic materials themselves, thereby affecting the ideality of devices. Therefore, the mechanism by which air atmosphere affects the ideality of organic field effect transistor devices still needs to bestudied.

The research group of Prof. Jiansheng Jie and Prof. Xiaohong Zhang from the Institute of Functional Nano and Soft Matter of Soochow University has systematically studied and revealed the mechanism of action of air atmosphere on the ideality of organic field effect transistors. They used organic single-crystal small molecule semiconductor as the active layer, and used BCB/PS polymer without interface trapping as the device insulating layer, thereby eliminating the internal defects of the material and the carrier trapping at the semiconductor/insulating layer interface, which is ideal for the device. sexual influence. Their research found that water and oxygen molecules in the air atmosphere can act as double-edged swords on p-type field effect transistors. On the one hand, the water and oxygen molecules in the air atmosphere can effectively dope the organic materials at the electrode interface, filling the defect states generated during the electrode evaporation process, thereby improving the carrier injection efficiency and improving the device ideality. On the other hand, with the prolonged exposure of the device to air, water and oxygen molecules will also adsorb and gradually enter the organic semiconductor channel, trapping minority carriers (electrons) injected under positive gate voltage, resulting in non-ideal device behavior. By selectively doping the interface of the device and controlling the atmospheric environment in the test, the non-ideal behavior of the device can be effectively eliminated, and a field effect transistor with ideal working characteristics can be realized.

   The researchers believe that this study has systematically revealed the effect of air atmosphere on the ideality of p-type organic field effect transistors, which not only helps to elucidate the factors of the performance evolution of field effect transistors in the air, but also can provide a basis for the construction of high-performance organic field effect transistors. Field effect transistors play a certain guiding role.

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