When sunlight shines on the semiconductor p-n junction, new hole-electron pairs are formed. Under the action of the built-in electric field of the p-n junction, holes flow from the n region to the p region, and electrons flow from the p region to the n region. When the circuit is connected, current is formed. This is the working principle of the photovoltaic effect solar cell.
There are two ways to generate solar power: one is the light-heat-electricity conversion method, and the other is the direct light-electricity conversion method.
(1) The light-heat-electricity conversion method generates electricity by utilizing the heat energy generated by solar radiation. Generally, the solar collector converts the absorbed heat energy into steam of the working fluid, which then drives the steam turbine to generate electricity. The former process is the light-heat conversion process; the latter process is the heat-electricity conversion process, which is the same as ordinary thermal power generation. The disadvantages of solar thermal power generation are low efficiency and high cost. It is estimated that its investment is at least 5 to 10 times more expensive than that of ordinary thermal power plants.
(2) Direct light-electricity conversion method This method uses the photovoltaic effect to directly convert solar radiation energy into electrical energy. The basic device for light-electricity conversion is the solar cell. Solar cells are devices that convert sunlight directly into electrical energy due to the photovoltaic effect. They are semiconductor photodiodes. When sunlight shines on the photodiode, the photodiode converts the sunlight into electrical energy and generates current. When many cells are connected in series or in parallel, they can form a solar cell array with relatively large output power. Solar cells are a promising new power source with three advantages: permanence, cleanliness and flexibility. Solar cells have a long lifespan. As long as the sun exists, solar cells can be used for a long time with a one-time investment. Compared with thermal power generation and nuclear power generation, solar cells do not cause environmental pollution.