Organic semiconductor materials, with their unique optical, electrical and magnetic properties, have shown broad application prospects in the fields of new organic field effect transistors (OFETs), organic light-emitting diodes (OLED) and organic photovoltaics (OPV). According to the materials of organic semiconductors, it can be divided into small molecule organic semiconductors, polymer organic semiconductors and donor-acceptor complex organic semiconductors. The charge transfer can occur between the donor molecule and the acceptor molecule, so that the material has semiconducting properties. Acceptor molecule refers to a molecule that can specifically bind to a substrate. In the field of electrochemistry, acceptor molecules refer to molecules that can accept electrons. Acceptor molecules are an important part of organic semiconductor materials. In semiconductor materials, acceptor molecules are required to have a low lowest unoccupied molecular orbital (LUMO)/highest occupied molecular orbital (HOMO) energy level. This will make it have strong electron-deficient properties, strong pull-out ability, excellent electron transmission properties and strong electron affinity. Organic semiconductor materials can adjust the properties of semiconductors by changing the structure of acceptor molecules, thereby improving the performance of semiconductor application devices.
Figure 1. Schematic diagram of active layer of donor-acceptor organic solar cell
- Organic field effect transistor (OFET): OFET is a three-electrode circuit switching element, which is an active device that controls the conductivity of organic semiconductors by regulating the gate voltage. Among many semiconductors, D-A organic polymer semiconductor materials can be widely used in OFET devices as materials with high mobility and high carrier transport. Common acceptor polymers are divided into p-type organic semiconductor materials, n-type organic semiconductor materials, and bipolar organic semiconductor materials. Common structures are polythiophenes, polythiazoles, iso-indigo, naphthimide, polycyclic fused aromatic hydrocarbons and so on. These molecules provide effective channels for high-performance charge transport due to their high electron-deficiency characteristics and good planarity, improve the electron and hole mobility of organic semiconductors, and optimize the performance of OFETs.
- Solar cell: In solar cells, organic semiconductor materials play an important role. The application fields of solar cells are also very wide, such as building integration, traffic lights, communications and so on. Organic molecules have a clear molecular structure, fixed molecular weight, higher purity, and better repeatability. In solar cells, D-A organic semiconductor materials have a wider absorption spectrum, better air stability, easy-to-adjust energy levels and optical properties. Regulating the structure of acceptor molecules can effectively control the properties of semiconductors, so that solar cells can absorb wider wavelengths of sunlight, and can also improve photoelectric conversion efficiency, so that solar cells can improve overall power generation efficiency. Among a series of acceptor molecules, perylene diimide is a type of n-type organic acceptor material that has received widespread attention and exhibits excellent photoelectric properties.
- B. Saibal,A. Z. Ashar,R. Nandini Devi,K. S. Narayan,S. K. Asha. Nanostructured Donor–Acceptor Self Assembly with Improved Photoconductivity [J]. ACS Appl. Mater. Interfaces 2014, 6, 21, 19434–19448.