Benzothiadiazole is a benzoquinone nitrogen-sulfur heterocyclic aromatic hydrocarbon. The presence of imine functional groups with relatively low energy level π-orbitals in this molecular structure endows benzothiadiazole with strong electron-withdrawing ability. A variety of benzothiadiazoles & analogs can be obtained by using benzothiadiazole as a structural unit to modify the molecular structure. The introduction of benzothiadiazole units into organic semiconductor materials can effectively tune the electronic structure, energy band structure and carrier transport properties of semiconductor materials, thereby achieving efficient charge transport. When designing benzothiadiazole-based materials, various donor groups are often added to construct donor-acceptor small molecule materials for application in the field of organic optoelectronics.
Figure 1. Benzothiadiazole Structural Unit
- Organic Field Effect Transistor (OFET): Benzothiadiazole has suitable HOMO (highest occupied molecular orbital), LUMO (lowest unoccupied molecular orbital) energy levels, and good molecular planarity, which is an important deficiency electronic unit D-A (donor-acceptor) molecular design. Such D-A molecules are arranged in a tilted manner, which can effectively reduce the mutual repulsion between electrons, enhance the intermolecular force and the coupling of electrons, and is conducive to the formation of tighter π-π stacking. This close packing facilitates the transfer of charges between molecules in a hopping manner, which ultimately contributes to the migration of carriers and improves the efficiency of OFET devices.
- Organic solar cells (OPV): As a typical acceptor unit, benzothiadiazole can form a D-A structure with molecules such as thiophene, pyrrole, and carbazole, thereby reducing the band gap, broadening the absorption, and improving the photoelectric conversion efficiency. These compounds are used as donor materials for solution processing to prepare OPV devices, which exhibit good optoelectronic properties and enhance the photoelectric conversion efficiency.
- Organic electroluminescent materials: Benzothiadiazoles are often used as the toning unit of light-emitting materials to construct small molecules or polymers to realize the regulation of the emission wavelength of light-emitting materials, the optimization of charge injection and transport properties. Such luminescent materials can be used in electroluminescent devices to enrich luminescent colors, improve photoelectric conversion efficiency, and enhance luminescent stability.
- Dahae Jung,Bodakuntla Thirupathaiah,Eunsoo Lee,Guhyun Kwon,Choongik Kim,SungYong Seo. Synthesis and Characterization of Benzothiadiazole Derivatives as Organic Semiconductors for Organic Thin-Film Transistors [J]. J. Nanosci. Nanotechnol., 2016, 16, 924-929.