As global energy sources become more and more stressed, solar power is called new energy development, and we use more solar cells in our lives. The solar cell is based on semiconductor materials. The absorption of light-electric material is followed by light energy and photo-electrical conversion, so that it generates current, what is the working principle of solar cell? A solar cell is a device that directly converts light energy into electrical energy through a photo-electric effect or a photo-electric effect. When the sun shines on a semiconductor, some of it is reflected off the surface and the rest is absorbed or transmitted by the semiconductor. Some absorbed light, of course, becomes heat, while other photons collide with valence electrons that make up semiconductors, Thus the electrons form the pore pair. Thus the light energy is converted into electrical energy in the form of electron-hole pairs. When the sunlight illuminates the pn junction, the electrons in the semiconductor release electrons due to the acquisition of light energy, accordingly the electron-hole pairs are generated, and under the action of the barrier electric field, induced towards the electron pattern field. Holes are driven towards the p-type region, so that the region has additional electrons, and the p region has extra holes. Thus, a photo-generated electric field is formed around the pn junction opposite the direction of the barrier electric field. If the semiconductor has a pn junction, then a barrier electric field is formed on both sides of the p-type and n-type interfaces which can drive electrons and holes in the n field to the p field, so that the extra electron in the n field, And there is an additional P field. The hole creates an output electric field of light opposite the direction of the electric field of the barrier near the PN junction. There are more than a dozen semiconductor materials for the manufacture of solar cells, and thus many types of solar cells. Currently, the most mature and commercially valuable solar cells are silicon solar cells. Below we introduce the principle of working solar cells in detail to take silicon solar cells as an example.