Organic semiconductor material is a kind of organic compound material whose conductivity is between organic insulator and organic conductor. At the beginning of the 21st century, by virtue of the outstanding achievements in the field of organic semiconductor materials, scientist Hideki Shirakawaa won the Nobel Prize in chemistry, which indicates that organic semiconductor materials have received high social attention. Due to adjustable molecular structure, easy processing and low toxicity, organic semiconductors are mainly applied as the components of optoelectronic devices.
- Organic solar cells: One of the earliest applications of organic semiconductors was solar cells that have been widely used due to their simple preparation process and low production cost.
- Organic thin-film transistor (OTFT): Organic thin-film transistor (OTFT) is the main application field of organic semiconductor materials. Organic thin-film transistor (OTFT) is an active device that uses electric field to control the conductivity of solid materials. Using organic thin-film transistor is expected to produce sensor and smart cards.
- Organic light-emitting diode (OLED): Organic light-emitting diodes (OLEDs) emit relying on organic semiconductor heterojunction. Because organic semiconductors are thin and flexible, they can be used as display devices in flexible substrates such as paper and cloth.
- The others: Flexible wearables devices can be prepared by using the flexibility of organic semiconductor materials, which will have great application prospects in electronic skin, biological detection, in vivo implant therapy, and other biomedical fields.
- Nitrogen heterocyclic semiconductor materials: Nitrogen heterocyclic semiconductor materials mainly include phthalocyanine compounds and azobenzene compounds. The key problems of low luminescence efficiency and low battery conversion efficiency can be solved by using the effects of macromolecular crystal, aggregation and self-assembly of phthalocyanine compounds. Besides, most of the phthalocyanine organic semiconductor materials are P-type semiconductor, but less N-type semiconductor.
Figure 1. The molecular structure of phthalocyanine.
- Sulfur-containing heterocyclic semiconductor materials: An example of sulfur-containing heterocyclic semiconductor materials is poly3-alkylthiophene. Due to multi-hole, high electron mobility, wide spectral response range and excellent environmental stability, poly3-alkylthiophene can be applied as donor or acceptor materials for organic polymer solar cells.
Figure 2. The molecular structure of poly3-alkylthiophene.
- Oxygen-containing aromatic ring semiconductor material: Furan is a typical representative of oxygen-containing aromatic ring semiconductor materials with reproducibility and environmental degradation properties. Furan and its derivatives, with blue fluorescence and high quantum efficiency, are ideal candidates for luminescent materials.
Figure 3. Molecular structures of organic semiconductor compounds with furan ring.
- Oxygen and sulfur-containing aromatic ring semiconductor material: Furan-thiophene quinoid organic semiconductor molecules are an example of such material. The material shows high electron mobility and the mobility of transistor devices manufactured by solution method is high.
Figure 4. Molecular structures of furan-thiophene quinoid molecules.
- Aromatic ring semiconductor material: Aromatic ring semiconductor material mainly refers to pyrene. The basic structural unit of pyrene molecule has four benzene rings. With the advantages of pure blue fluorescence, long fluorescence life, high carrier mobility, pyrene can meet the basic conditions for the construction of organic photoelectric material.
- Hu Y, Gao X, Di C A, et al. Core-Expanded Naphthalene Diimides Fused with Sulfur Heterocycles and End-Capped with Electron-Withdrawing Groups for Air-Stable Solution-Processed n-Channel Organic Thin Film Transistors[J]. Chemistry of Materials, 2011, 23(5):1204-1215.