In common electronic device products, organic semiconductors are important core components. For example, the performance of electronic devices such as organic field-effect transistors, organic photovoltaic cells, organic light-emitting diodes, and organic thermoelectric elements depends on the performance of organic semiconductors. In terms of molecular weight, organic semiconductors can be divided into small molecular materials and polymer/macromolecular materials. Polymer/macromolecular semiconductor materials occupy an important position in the field of electronics due to their advantages of good film formation, solution processability, flexibility, and diverse structures. For the modification of polymer/macromolecular semiconductor materials, the introduction of different electron-withdrawing or electron-donating groups is a good strategy. Donor monomers are compounds with electron-donating properties that can be introduced into the polymer/macromolecular backbone (donor-donor type) as electron-donating groups or side-chain groups to modify the structure and properties of semiconductor materials. Common donor monomers are small molecules such as benzene rings and thiophenes.
Figure 1. Molecular structures of some common donor monomers
- P-type organic semiconductor materials: A P-type semiconductor is a material that mainly transports holes. This type of material has a relatively high HOMO (Highest Occupied Molecular Orbital) energy level and is relatively stable in air. The fused-ring aromatic hydrocarbon polymer with benzene ring as the structural unit, benzene ring as the donor monomer, evenly distributed π electrons in the molecule, has strong intermolecular interaction, and can be used to prepare thin film devices. The donor monomer thiophene ring is also suitable for the preparation of P-type organic semiconductor materials. There is a lone pair of electrons on the sulfur atom in the thiophene ring, which makes the thiophene ring have a high charge density. Using thiophene derivatives as donor monomers can adjust the electron distribution orbits of polymers/macromolecules, reduce molecular energy levels, increase molecular band gaps, and increase the steric stability of semiconductor materials. It can be seen that the polymer/macromolecular semiconductor material containing the donor monomer is a kind of P-type organic semiconductor with high hole transport rate and good stability, which can be used for the preparation of thin-film organic field effect transistors, light-emitting diodes and other electronic devices.
- Yulun Wang,Qiaogan Liao,Gang Wang,Han Guo,Xianhe Zhang,Mohammad Afsar Uddin,Shengbin Shi,Huimin Su,Junfeng Dai,Xing Cheng,Antonio Facchetti,Tobin J. Marks,Xugang Guo. Alkynyl-Functionalized Head-to-Head Linkage Containing Bithiophene as a Weak Donor Unit for High-Performance Polymer Semiconductors [J]. Chem. Mater. 2017, 29, 9, 4109–4121.