Semiconductor materials refer to a class of materials with conductivity between conductors and insulators. The application of semiconductor materials is very wide, and different application fields use different properties of semiconductor materials. The thermistor uses the conductivity of semiconductor materials to increase rapidly with temperature. Diodes and triodes use impurity doping to form a PN junction (a space charge region formed between a P-type semiconductor and an N-type semiconductor) to promote charge transfer. Photoresistors are made by using the electrical properties of semiconductor materials to change with light. Furthermore, the semiconductor substrate can realize the production of several kinds of components on one chip to produce integrated circuits of various scales. These different characteristics make semiconductors have a variety of uses. According to the composition, semiconductor materials can be divided into elemental semiconductors, inorganic compound semiconductors, organic compound semiconductors, and amorphous and liquid semiconductors. At present, organic compound semiconductors are developing rapidly due to their advantages such as simple preparation, low cost, and strong controllability. Organic compound semiconductors can be divided into small molecule semiconductors and polymer/macromolecule semiconductors. Today, semiconductor materials are used to prepare solar cells, organic transistor (OFET), organic light-emitting diodes (OLED), displays, sensors and other devices, and are widely used in household appliances, communications, industrial manufacturing, aviation, aerospace and other fields.
Figure 1. Application of semiconductor materials
- Solar cell: The photovoltaic effect of semiconductor materials is the basic principle of the operation of solar cells. The main manufacturing material of solar cells is semiconductor materials, and the photoelectric conversion rate is the main factor for judging the quality of solar cells. According to the different semiconductor materials used, solar cells are divided into crystalline silicon solar cells, thin-film cells, and III-V group compound cells. The conversion efficiency of monocrystalline silicon cells is generally 14% to 17%. The highest conversion efficiency of polysilicon cells can reach 19.8%. Thin-film batteries have low cost, are mainly made of organic semiconductor materials, and have a moderate conversion efficiency. Group III-V compound battery has good radiation resistance and high conversion efficiency, making it the most ideal semiconductor photovoltaic material.
- Organic transistor (OFET): The use of OFET can produce a variety of superior performance sensors, smart cards, liquid crystal displays and flat panel display drivers, various disposable storage devices, computer peripheral display control switch arrays, etc. At the same time, the use of OFET can also promote the research on the electrical properties (conductivity, mobility, etc.) of the organic semiconductor material itself, so as to provide a basis for the synthesis of organic semiconductor materials with better performance.
- Organic Light Emitting Diode (OLED): In OLED devices, semiconductor materials generally have a π-π conjugated double bond structure, which can generate stable excitation and free migration carriers, and exhibit stable electrical conductivity. OLED devices are widely used in displays, lighting and various drivers, and have the advantages of wide field of view, ultra-thin, fast response, and high luminous efficiency.
- Sensor: Applying the conductivity and energy transfer of semiconductor materials to the sensor can produce a synergistic response effect and obtain high sensitivity. The sensor can also be further miniaturized, so that it has the characteristics of high precision, high integration, and high intelligence.
- Zhenwei Wang, Pradipta K. Nayak, Jesus A. Caraveo-Frescas, Husam N. Alshareef. Recent Developments in p-Type Oxide Semiconductor Materials and Devices [J]. Advanced Materials, 2016, 28, 3831-3892.