What is the photovoltaic effect?
This is the mechanism by which light can be converted into electricity and is used in the solar power industry to generate power. We will not go into the quantum mechanical explanation here, but here is a simple explanation of how the photovoltaic (PV) effect works:
- Two semiconductors are connected to each other: one n-type and one p-type. These semiconductors are doped with certain elements to make them negatively charged (n-type) or positively charged (p-type). Since opposite charges attract to minimize potential energy, the electrons and holes come together to form a middle section called the depletion zone. Here, an electric field forms which prevents the charges from moving to opposite sides.
- In order to generate power, these charges need to be moving. Sunlight comes down in packets of energy called photons (at least in the model we’ll be using). These photons have enough energy to knock the charges from the depletion zone.
- Now the depletion zone is unbalanced. The electrons need to cross over to the p-side and the holes over to the n-side to neutralize the charges. It is important to note that during all of these steps, the Sun is constantly bombarding the semiconductors with photons.
- The charges move across oppositely charged semiconductors. The charges that make it through the wire in the circuit (not shown) generate the current. Some charge carriers combine with the opposite charges. This is known as recombination. Again and again, photons bombard the semiconductors and the cycle repeats.