Pyrimidine is a diazine compound formed by replacing two carbon atoms in the meta position of benzene with two nitrogen atoms. Pyrimidines are aromatic organic molecules containing both π-conjugated systems and nitrogen heteroatoms. Pyrimidines has good absorption characteristics and large Stoke shift in the visible light region, and the desired optoelectronic properties can be obtained by molecular design. The electron-deficient nature of the pyrimidine unit makes it have a higher electron affinity and is suitable as an electron transport unit. In addition, the pyrimidine unit has a certain basicity and can be used as a ligand unit to form a complex to modify the optoelectronic properties of the molecule. Based on the above advantages, pyrimidines small molecule semiconductor materials are often used in optoelectronic devices such as organic electroluminescent devices (OLEDs), organic thin film transistors (OFETs), and organic solar cells (OPVs).
Figure 1. Chemical structures of pyrimidine
- Organic Electroluminescent Devices (OLED): Pyrimidine compounds have excellent optoelectronic properties and modifiability, and are often used to design and construct host materials for OLEDs. Doping pyrimidine compounds into the host material can improve the emission quantum efficiency, reduce the startup voltage, increase the external quantum efficiency, and enhance the injection and transport of electrons in the OLED material.
- Organic Thin Film Transistors (OFETs): In the transport material of OFET, the presence of pyrimidine units improves the electron affinity of the material and can stabilize the HOMO (Highest Occupied Molecular Orbital) energy level of the material. Pyrimidine-based electron transport materials have high electron mobility, excellent film-forming properties, and morphology stability, which can improve the efficiency of OFETs.
- Organic solar cells (OPV): Pyrimidine-containing π-systems are favorable for the formation of planar structures and provide efficient intramolecular charge transfer, which can be applied to OPV materials. The materials containing pyrimidine groups enhance the absorption of the red part of sunlight, so that the energy conversion efficiency and open circuit voltage of OPV are enhanced, and the device performance of OPV is improved.
- Ryutaro Komatsu, Hisahiro Sasabe, Junji Kido. Recent progress of pyrimidine derivatives for high-performance organic light-emitting devices [J]. J. Photonics Energy, 2018, 8, 032108.