Organic field effect transistor (OFET) is an active device that uses π-conjugated organic small molecules or polymers as semiconductor materials and regulates the conductivity of the semiconductor layer through the gate. Organic semiconductor materials are an important part of OFETs, which play the role of carrier generation, injection and transport. The intrinsic properties of the material determine the speed and stability of carrier migration, and thus determine the performance of the device. It is generally believed that organic semiconductor materials suitable for OFET should have the following characteristics: large π-conjugated system, strong intermolecular forces, suitable molecular energy levels, and good thermal and chemical stability. During the operation of the device, the material in which the carriers in the conductive channel formed on the interface of the insulating layer of the semiconductor layer are holes is a p-type organic semiconductor. P-type organic semiconductors have relatively high mobility and exhibit good air stability. Common p-type organic semiconductors mainly include aromatic fused rings, oligothiophenes, tetrathiafulvalenes (TTF), phthalocyanines and other small molecule materials, polythiophenes, donor-acceptor (DA) copolymers and other polymer materials.
Figure 1. Common p-type organic semiconductor
- Gas sensor: Thin films made of phthalocyanine small molecules in p-type organic semiconductor materials can be used as OFET transistors in gas sensors. The copper phthalocyanine film made by vacuum evaporation can be used as NO2 sensor. When the relative humidity is not zero, the lowest limit for detecting NO2 can be less than 50ppb, and it has a good response sensitivity. It can be seen that p-type organic semiconductors can be prepared into thin films and used in gas sensors to achieve high-sensitivity response.
- Flexible display area: OFET has the advantages of fast electronic transmission speed and excellent photoelectric performance, and can be used in the field of flexible display. The p-type organic semiconductor material is vapor-deposited on the gate electrode as an organic layer, which can further improve the carrier transport ability. And it has good adaptability to the polymer of the flexible substrate, and realizes the application in the fields of low-cost, large-area flexible display, flexible integrated circuit and so on.
- Integrated circuit: Atmospheric testing found that the environment has relatively little influence on the hole transport performance of p-type organic semiconductor materials, so its stability is generally good. Such stability makes it easier to fabricate an array-type integrated circuit by a simple method. In addition, p-type organic semiconductors have good solubility, and most of the organic micro-nano single crystal arrays prepared by the solution method exhibit good hole mobility, which promotes the application of large-scale integrated circuits.
- Shuqiong Lan, Yujie Yan, Huihuang Yang, Guocheng Zhang, Yun Ye, Fushan Li, Huipeng Chen, Tailiang Guo. Improving device performance of n-type organic field-effect transistors via doping with a p-type organic semiconductor [J]. J. Mater. Chem. C, 2019, 7, 4543-4550.