Solar cell is the use of the photoelectric effect of semiconductor materials, device for converting solar energy into electrical energy. Light born v effect: assume that light on the solar battery and the light at the interface layer being accepted, with enough energy photons can in p-type silicon and n-type silicon electronics from covalent bond, electron - hole on the attack. The electric field results of adjacent electrons and holes in the interface layer are separated from each other by space charges before recombination. Electrons move to the positively charged N region and holes to the negatively charged P region. Charge separation through the interface layer will generate an outward testable voltage between the P and N regions. At this point, electrodes can be added to both sides of the silicon wafer and connected to the voltmeter. For crystalline silicon solar cells, the typical value of open circuit voltage is 0.5 ~ 0.6v. The more electron-hole pairs occur at the interface through light, the greater the current. The more light energy the interface layer receives, the larger the interface layer, i.e. the larger the battery area, and the greater the current composed in the solar cell.
1.Power generation principle
The sun shines on the semiconductor p-n junction, forming a new hole-electron pair. Under the action of the electric field at the p-n junction, the hole flows from the n region to the p region, and the electron flows from the p region to the n region. This is how photovoltaic solar cells work.
Solar power generation there are two ways of solar power generation, one is the light-heat-electricity conversion mode, the other is the direct light-electricity conversion mode.
(1) the light-thermal-dynamic-electric conversion mode generates electricity by utilizing the thermal energy generated by solar radiation. Generally, the solar collector converts the heat energy absorbed into working medium steam and drives the steam turbine to generate electricity. The former process is the light-heat conversion process; The latter process is the final conversion process from thermal power to electricity, which is the same as ordinary thermal power generation. The disadvantage of solar thermal power generation is low efficiency and high cost, which is estimated to be at least 5-10 times more expensive than ordinary thermal power generation.
(2) direct light-electricity conversion mode this mode USES the photoelectric effect to convert solar radiation energy into electric energy directly. The basic device of light-electricity conversion is solar cell. Solar cell is a kind of device that directly converts solar light energy into electric energy due to the photovoltaic effect. It is a semiconductor photodiode. When the solar light hits the photodiode, the photodiode will change the solar light energy into electric energy and generate current. When many cells are connected in series or in parallel, they can become solar arrays with relatively large output power. Solar cell is a promising new type of power source with three advantages of permanence, cleanness and flexibility. Compared with thermal power generation, solar cells do not cause environmental pollution.
2.The advantages and disadvantages
Compared to conventional power generation systems
Solar power generation is called the most ideal new energy. (1) no risk of depletion; (2) safe and reliable, no noise, no pollution emissions, absolutely clean (no pollution); (3) not limited by the distribution of resources, can use the advantage of building roof; (4) local power generation and supply without the consumption of fuel and transmission lines; (5) high energy quality; Users are emotionally receptive; 7 build cycle is short, the time that obtains energy is short.
(1) the energy distribution density of irradiation is small, that is, it takes up a huge area; The obtained energy is related to four seasons, day and night, rain or shine and other meteorological conditions. In terms of current science and technology, using solar energy to generate electricity costs a lot, but the utilization rate of solar energy is low, so it cannot be widely used. Currently, it is mainly used in some special environments, such as satellites.