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Introduction of solar cell materials and semiconductor materials
- Jun 01, 2018 -

Solar power is currently the industry's leader in the field of clean energy. If you are interested in it, take you to understand the composition of solar cells and related photovoltaic materials.


Solar power plants, commonly referred to as solar cells, can directly convert sunlight energy into electricity. In solar panels, the photons released by the sun cause the outer electrons of the semiconductor material to be free from the bonds of atomic bonds. When the electrons are forced to move in the same direction, they can generate electricity to power electronic devices or deliver electricity to the grid.


Since the French physicist Alexandre-Edmond Bequerel first theoretically photovoltaicized electricity in 1839, photovoltaic power generation has been one of the topics in the field of scientific research. At present, with the major research teams in the United States, Japan, and Europe accelerating the industrialization of their respective solar energy systems, the international market for the photovoltaic industry continues to expand.


Photovoltaic modules


Although the photovoltaic power generation system has various constituent materials, all the components include several layers of material from the smooth side to the backlight side. Sunlight first passes through the protective layer (usually glass) and then enters the inside of the battery through the transparent contact layer. At the center of the assembly is an adsorbent material, which absorbs photons and completes the "photocurrent". The semiconductor material contained therein depends on the requirements of the specific photovoltaic system.


Below the adsorbent layer material is a back metal layer that completes the conduction of the circuit. The composite film layer is under the back metal layer, and its function is to make the photovoltaic module waterproof and heat-insulating. Generally, an additional protective layer is added on the back of the photovoltaic module. The protective layer material is glass, aluminum alloy or plastic.


Semiconductor material


The semiconductor material in the photovoltaic power generation system may be silicon, a polycrystalline thin film, or a single crystal thin film. Silicon materials include monocrystalline silicon, polysilicon, and amorphous silicon. Monocrystalline silicon has a regular structure, which has a higher photoelectric conversion rate than polysilicon.


Silicon atoms in amorphous silicon are randomly distributed, and their photoelectric conversion efficiency is lower than that of single crystal silicon. However, compared with crystalline silicon, it can capture more photons while adding germanium or carbon to amorphous silicon. Alloying can enhance this feature.


Copper indium diselide (CIS), cadmium telluride (CdTe) and thin-film silicon are common polycrystalline thin-film materials, while materials with higher photoelectric conversion, such as gallium arsenide (GaAs), often contain single crystals. Crystalline silicon thin film material. All of the above materials are used in a specific photovoltaic power generation field because of their unique properties. These properties include: crystallinity, band gap size, absorption properties, and ease of processing.


External factors affect semiconductors


The order of the atoms in the crystal structure determines the crystallinity of the semiconductor material, and the charge transport, current density, and energy conversion efficiency of the solar cell are all affected by the crystallinity. The bandgap of a semiconductor material is the minimum energy required to transition electrons from a bound state to a free state (ie, allowing electron conduction). The band gap size is usually expressed in Eg, which describes the energy difference between the valence band and the conduction band. The valence band of semiconductor materials is a low energy level and the conduction band is a high energy level. The absorption coefficient is used to characterize the distance of a photon penetrating medium at a particular wavelength, which determines the ability of the photon to be absorbed by the medium. The absorption coefficient is determined by the cell material and the wavelength of the absorbed photons.


The cost and ease of processing of various semiconductor materials and devices depends on a variety of factors, including the type of materials and scale of use, the production cycle, and the migration characteristics of the cells within the deposition chamber. Each of these factors will play an important role in the specific demand for photovoltaic power generation.