Sunlight shines on a semiconductor p-n junction, forming new electron-hole pairs. Under the influence 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, forming an electric current when the circuit is connected. This is the working principle of a solar cell based on the photoelectric effect.
Direct photo-to-electricity conversion utilizes the photovoltaic effect to directly convert solar radiation energy into electrical energy. The basic device for this conversion is the solar cell. A solar cell is a device that directly converts solar energy into electrical energy due to the photovoltaic effect. It is a semiconductor photodiode. When sunlight shines on the photodiode, it converts the sunlight into electrical energy, generating an electric current. Many cells connected in series or parallel can form a solar cell array with a relatively large output power. Solar cells are a promising new type of power source with three major 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.
The main specific principle of a photovoltaic power generation system is the photoelectric effect of semiconductors. When a photon strikes a metal, its energy can be completely absorbed by an electron within the metal. If the absorbed energy is large enough, the electron can overcome the internal attraction of the metal, escape from the metal surface, and become a photoelectron. Silicon atoms have four outer electrons. If atoms with five outer electrons, such as phosphorus atoms, are added to pure silicon, it becomes an N-type semiconductor; if atoms with three outer electrons, such as boron atoms, are added, a P-type semiconductor is formed. When P-type and N-type semiconductors are combined, a potential difference is created at the interface, forming a solar cell. When sunlight shines on the P-N junction, holes move from the P-region to the N-region, and electrons move from the N-region to the P-region, creating an electric current.