Electroluminescent materials can convert electrical energy directly into light energy, and can glow when running a current through them. Electroluminescent materials have a broad emission spectrum that can be classified as blue range, green range, red range and so on. Electroluminescent materials generally need to produce into devices for application, and the structure of the electroluminescent device is shown in figure 1.
Figure 1. The structural of electroluminescent material device.
Electroluminescent materials have the characteristics of low energy consumption and small size, which is very promising in the areas of screen display, and aerospace.
- Television and computer display: Taking the advantages of high brightness, wide viewing angle, high contrast and bright colors, electroluminescent materials are very suitable for the preparation of HD displays.
- Communication terminal and instrument display: The working voltage and energy consumption of electroluminescent materials are low, which is very suitable for the occasion with narrow working space. It has been applied in the instrument display of automobile and motorcycle.
- Aerospace field: Due to high shake-resistance and good environmental tolerance, electroluminescent materials can be used in the areas of aerospace.
Electroluminescent materials can be divided into inorganic and organic materials. Inorganic electroluminescent materials have a long history and are the earliest materials recognized and applied by human beings. Moreover, organic electroluminescent materials have been developed rapidly recently, due to their high luminous efficiency and low energy consumption.
Figure 2. The classification of electroluminescent materials.
- Inorganic electroluminescent materials: This kind of materials can be divided into ZnS based electroluminescent materials, SiO2 based electroluminescent materials and blue electroluminescent material. Among them, ZnS:Mn is one of the earliest studied electroluminescent materials. The luminescent band spectrum ranges from 540 nm to 680 nm and the peak is 585 nm with orange color. SiO2:Ge is a representative of SiO2 based electroluminescent materials. The electroluminescent device prepared by this material has a very wide EL(Electroluminescence) spectrum and its peak is in the infrared band. Furthermore, due to the short-wavelength of blue light, blue electroluminescent materials have high requirement for substrates. The materials with good performance are SrS:Ce, MGa2S4(M=Ca,Sr,B):Ce and SrS:Cu.
- Organic electroluminescent materials: Organic electroluminescent materials can be divided into electroluminescent materials based on metal complex and polymer electroluminescent materials. As for electroluminescent materials based on metal complex, the metal element can be Ru2+, Be2+, Zn2+, Al3+, Ga3+, Eu3+ and Gd3+. It can be classified into 8-hydroxyquinolines, 10-hydroxybenzoquinolines, Schiff base metal complexes and rare-earth complex. In addition, the classification of polymer electroluminescent materials is conjugated polymer, polymer containing metal complexes and doped polymer.
Figure 3. Examples of polymer electroluminescent materials.
- Slinker J, Bernards D, Houston P L, et al. Solid-state electroluminescent devices based on transition metal complexes[J]. Chemical Communications, 2003(19):2392-2399.
- Peng Q, Lu Z Y, Huang Y, et al. Novel efficient green electroluminescent conjugated polymers based on fluorene and triarylpyrazoline for light-emitting diodes[J]. Journal of Materials Chemistry, 2004, 14(3):396-401.