Photovoltaic power generation is based on the "photovoltaic effect." When light, in the form of photons, hits a material like metal, some of the electrons within that material can absorb the energy from the photons. If the energy is sufficient, these electrons can overcome the binding force of the metal and escape as photoelectrons.
This process creates a potential difference between different parts of a semiconductor or between a semiconductor and a metal. It starts with converting light into electrical energy—light waves are transformed into free electrons. Then, a voltage is generated, similar to building a dam. When the two ends are connected, an electric current flows through the circuit.
The core principle behind photovoltaic power generation is the photoelectric effect in semiconductors. A silicon atom has four valence electrons. When it's doped with atoms like phosphorus (which has five electrons), it becomes an N-type semiconductor, which carries a negative charge. On the other hand, doping silicon with boron (which has three electrons) results in a P-type semiconductor, carrying a positive charge. When N-type and P-type materials are joined, a PN junction is formed, creating a solar cell. When sunlight strikes this junction, electrons move from the P-side to the N-side, while holes move in the opposite direction, generating an electric current.
After the polycrystalline silicon is refined, cut into ingots, and sliced, it becomes a silicon wafer. A PN junction is created by doping the wafer with small amounts of elements like boron or phosphorus. Then, screen printing is used to apply fine silver paste onto the surface, forming a grid pattern. This grid acts as a conductor, and during sintering, a back electrode is also formed. An anti-reflective coating is applied to the front surface to increase efficiency. These processed wafers are then assembled into modules. The module is enclosed in an aluminum frame, covered with glass on the front, and mounted with electrodes on the back. With additional components like a current inverter, the system can generate usable electricity.
Once the electricity is generated, it can be stored in batteries or fed into the power grid. In terms of cost, solar panels make up about half of the total expense, while inverters, installation, and other components account for the remaining half. Overall, photovoltaic systems offer a clean, renewable, and increasingly efficient way to generate electricity from sunlight.
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