Solar panels are devices that use the photovoltaic effect to convert sunlight into electrical energy. Its operating principle is as follows:

1. Photovoltaic effect: The photovoltaic effect refers to the absorption of photon energy by electrons when light shines on semiconductor materials, causing electrons to jump from the valence band to the conduction band, generating electron-hole pairs. In this way, electron and hole flows are formed in the semiconductor, thereby generating current.

2. PN junction: Solar panels are usually composed of two layers of differently doped semiconductor materials to form a PN junction. Among them, the P region is rich in positive charges (holes) and the N region is rich in negative charges (electrons).

3. Light absorption: The surface of the solar panel is covered with a light absorption layer, which is usually made of silicon material. When sunlight shines on the light absorption layer, the energy of the photon is absorbed, exciting electron-hole pairs.

4. Charge separation: The electron-hole pairs excited by light will be separated under the action of the electric field of the PN junction. Electrons will move to the N region and holes will move to the P region, forming a current.

5. Current output: By connecting wires, current is drawn from the positive and negative poles of the solar panel, which can be used for power supply or storage.

In summary, the operating principle of solar panels is to use the photovoltaic effect to convert sunlight into electrical energy, and to separate the photoexcited electron-hole pairs through the electric field of the PN junction to form current output.