The basic principle of solar photovoltaic power generation is to use the photovoltaic effect of solar cells to directly convert the solar radiation energy into electrical energy. The energy converter of solar photovoltaic power generation is the solar cell, also known as photovoltaic cell. Photovoltaic cells are actually a large area of silicon semiconductor devices. The positive charge represents the silicon atom, and the negative charge represents the four electrons surrounding the silicon atom. When boron or phosphorus impurities (elements) are doped into the semiconductor silicon crystal, because there are only three electrons around the boron atom and five electrons around the phosphorus atom, a crystal structure with holes and a crystal structure with excess electrons as shown in Figure 1-2 will be generated, forming a P-type or N-type semiconductor.
Because P-type semiconductor contains more holes and N-type semiconductor contains more electrons, when P-type and N-type semiconductor form a special thin layer at the interface of the two semiconductors, the P-type side of the thin layer is negatively charged, and when combined, the type side is positively charged, forming a PN junction.
When the sunlight shines on the photovoltaic cell, part of the light is reflected, part of the light is absorbed, and part of the light passes through the cell. The absorbed light energy excites the electrons in the bound high energy level state to produce an electron hole pair. Under the action of the built-in electric field of the PN junction, the electrons and holes move together, the holes in N area move to P area, and the electrons in P area move to N area, so that a large amount of negative charges (electrons) accumulate on the light receiving surface of the solar cell, while a large amount of positive charges (holes) accumulate on the backlight surface of the solar cell. If a load is connected to both ends of the battery, there will be a current flowing through the load. When the light is always shining, there will be a continuous flow of current flowing through the load. A single solar cell is a thin semiconductor PN junction. Under standard lighting conditions, the rated output voltage is 0.5~0.55V. In order to obtain higher output voltage and larger power capacity, in practical applications, it is often necessary to connect multiple solar cells together to form a battery module, or use more battery modules to form a photovoltaic array, as shown in Figure 1-5. The output power of the solar cell is random. The output power of the same solar cell is different at different times, different places, different light intensities, and different installation methods.