Polymer/macromolecular semiconductor materials are widely used in organic electronic devices due to their molecular design diversity and mechanical flexibility. Donor-acceptor (DA) conjugated polymers are a class of semiconducting polymers/macromolecular materials formed by alternate conjugation of donor units and acceptor units. The biggest advantage of DA polymer/macromolecular semiconductor materials lies in the tunability of their own properties, which can improve solubility, photophysical properties, electrochemical properties, crystallinity, etc. by adjusting the structure of donors, acceptors and side chains. And because of the intramolecular and intermolecular "push-pull" effect between the donor and acceptor units. This effect can effectively improve the stacking mode in the polymer film, so that the unitary stacking of the polymer is more compact and orderly, and thus has higher device performance. The properties of semiconductor materials can be well regulated by changing the DA structure inside the polymer/macromolecule, which plays an important role in organic field effect transistors and organic diodes. In addition, by adjusting the ratio of its internal donor and acceptor, the polymer/macromolecular band gap can be regulated, and a low band gap material can be fabricated, which has important applications in organic solar cells.
Figure 1. Chemical structures of some polymer/macromolecular semiconductors with DA type monomers
- Chemical sensor: Chemical sensors based on organic thin film transistors are widely used in environmental monitoring, industrial production, food safety and other fields. Oxygen is an extremely important component of natural life, and its detection plays an important role in many fields such as health, medicine, industrial safety, and the environment. Based on this, the D-A conjugated polymer semiconductor containing pyridine can be used as a sensing thin film layer to prepare a transistor, which can improve the sensitivity of the device to oxygen. Meanwhile, the introduction of electron-deficient (acceptor) units into the conjugated framework can effectively reduce the energy of the Highest Occupied Molecular Orbital (HOMO), thereby improving the environmental stability of the sensor.
- Organic thin film semiconductor materials: The organic thin film semiconductor layer can be prepared by vacuum thermal evaporation method or solution method. The polymer/macromolecular material has good solubility and can be prepared by a simple solution method without complicated experimental techniques and equipment. Polymer/macromolecular semiconductor materials with DA type monomers can be used as ambipolar semiconductors in electronic devices to increase electron transport efficiency. In addition, the advantages of polymer/macromolecular materials in thin film and miniaturization can be used in flexible display, flexible electronic circuits and other fields.
- Bipolar semiconductor materials: Bipolar materials can transport both electrons and holes, which is beneficial to the production of low-cost flexible electronic devices. Bipolar semiconductor materials must have a narrow band gap to obtain excellent performance. By constructing DA type polymers, the molecular structure and energy levels of the compounds can be regulated, and ambipolar semiconductor materials with narrow band gaps and high electron and hole transport efficiency can be obtained.
- Yankang Yang, Zhiguo Zhang, Haijun Bin, Shanshan Chen, Liang Gao, Lingwei Xue, Changduk Yang, and Yongfang Li. Side-Chain Isomerization on an n-type Organic Semiconductor ITIC Acceptor Makes 11.77% High Efficiency Polymer Solar Cells [J]. J. Am. Chem. Soc. 2016, 138, 45, 15011–15018.