The main principle of photovoltaic power generation is the photoelectric effect of semiconductors. When a photon shines on a metal, its energy can be absorbed by an electron in the metal. The energy absorbed by the electron is large enough to overcome the Coulomb force inside the metal atom and escape from the metal surface to become a photoelectron. Silicon atoms have four outer electrons. If pure silicon is doped with atoms with five outer electrons, such as phosphorus atoms, it becomes an N-type semiconductor. If pure silicon is doped with atoms with three outer electrons such as boron atoms, a P-type semiconductor is formed. When the p-type and N-type are combined, the contact surface will form an electric potential difference and become a solar cell. When the sun shines on the P-N junction, the current flows from the P-type side to the N-type side, forming a current.
The photoelectric effect is an important and amazing phenomenon in physics. Under the irradiation of electromagnetic waves higher than a certain frequency (the frequency is called the threshold frequency), the electrons inside some substances absorb energy and escape to form current, that is, photoelectricity.
After ingot casting, ingot breaking and slicing, polycrystalline silicon is made into silicon wafers to be processed. P-N junctions are formed by doping and diffusing trace amounts of boron, phosphorus, etc., on silicon wafers. Then, the screen printing is used to print the fine silver paste on the silicon wafer to make a grid line. After sintering, the back electrode is made at the same time, and a layer of anti-reflection coating is coated on the surface of the grid line, and the battery is made. The battery pieces are arranged and combined into battery components to form a large circuit board. Generally, the assembly is surrounded by an aluminum frame, the front is covered with glass, and the back is installed with electrodes. With the battery components and other auxiliary devices, the power generation system can be composed. To convert DC to AC, a current converter needs to be installed. After generating electricity, it can be stored by battery or input to the public grid. Battery components account for about 50% of the cost of the power generation system, and current converters, installation costs, other auxiliary components, and other costs account for the other 50%.