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Semiconductor Materials And Theory

Author: Source: Datetime: 2016-09-13 18:34:37
Solar cells based on semiconductor materials based energy conversion function having a semiconductor device like solar power portable generator. To this date, with the integrated circuit, as overwhelmingly dominant market solar battery material is silicon-based. Is a comprehensive and systematic understanding of the solar battery, it is necessary for semiconductor materials, especially silicon material to make the necessary understanding.

Doping characteristics

Incorporation of trace impurities (the doping) can significantly alter the conductivity of the semiconductor. Impurities can cause a change in carrier concentration changes, along with the semiconductor material resistivity change dramatically. The incorporation of different types of impurities of the same material, you can get different conductivity type semiconductor material indium.

Temperature characteristics

Temperature could significantly alter the conductivity of the semiconductor material. In general, the conductivity of semiconductors increases rapidly with increasing temperature, the semiconductor Hugh resistivity has a negative temperature coefficient, and the resistivity of the metal having a positive temperature coefficient, and the very slow change with temperature.

Environmental Characteristics

Conductivity of semiconductors will change with the light (called photoconductive phenomenon) occurs. In addition, the semiconductor conductivity also with the environment in which the electric field, magnetic field, pressure, and atmosphere and the like.
Conductive semiconductor characteristics available semiconductor band theory to explain substance composed of atoms, and atoms along with a positively charged nucleus and a number of motion around the nucleus of negatively charged electrons. The nucleus of positive charges and the charge is the same as the number of extranuclear. Nuclei such as typical semiconductor material such as silicon 14 has a positive charge, electrons around the core 14. Different orbital electron from the nucleus of different distance, suffered gravity is different, and therefore the energy is different portable solar power generator. Electronic suffered from binding nuclei near strong electron itself has little energy; and the outermost orbital electrons by binding the weakest, electrons have the energy, and therefore vulnerable to external action, and get rid of nuclei bound to become free electronic.

Outermost silicon atom has four electrons. Each electron shell can be seen as an electron energy level. Innermost layer has two quantum states, followed by layer 8 Takako state, the outermost layer also has eight quantum states. But only the outermost layer of silicon has four electrons, so there are four empty empty level or quantum states. Once the inner electron transitions may get the energy level up to these empty.

Usually a crystal silicon material, the energy band from visible crystals, since there are crystal Movement electron orbital overlap atoms and electrons, so that the same level of N atoms in the crystals isolated split into N energy slightly different different energy levels, so as to form a band. Each level of each band corresponding to a single atom. Low energy electron energy bands are often filled. Those who are electronically filled band filled band is called. Gao with full energy the most, that is filled valence electron band is called the valence band. Empty the lowest energy band, that band from the valence band recently called conduction band. Each band can exist between band area called band gap. Commonly referred to as the forbidden band is the conduction band minimum and valence band energy gap between the top of their energy difference is called the band gap (Eg), referred to the band gap, which reflects the electron from the valence band to the conduction band needed energy of. From the band theory, the metal band gap is very narrow or valence band and the conduction band overlap, and the band gap of the insulating material is very wide, generally 5eV above, while conventional band gap semiconductor material generally 5eV less.
Pure silicon is a semiconductor, that is, as compared with a metal having good conductivity (silver, copper, aluminum, etc.) of low conductivity material. This conductive material is very obvious and temperature. The outer shell of a silicon atom has four electrons,lifePo4 batteries which determine the physical and chemical properties on the nature of the valence electrons. Each silicon atom in the crystal through four valence electrons and four adjacent atoms combine to form a bond, i.e., a covalent bond. Since the bonding is secured relative to outer electrons ordered state, in the crystal can not be used for charge transport. Close to absolute zero, ie 0K = - 273 ° C, pure silicon is an insulator. Through the input can children (such as heat, light) electron binding may be corrupted, so that electrons are released at higher temperatures and moving within a certain range, the current can be formed in the crystal in the crystal.

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