What is the photovoltaic effect?
This is the mechanism by which light can be converted into electricity and is used in the solar industry to generate power. 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 region. 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 material and generate an electron-hole pair (EHP).
- The EHPs generated in the depletion region are in an electric field and are thus pushed away. Holes flow with the field, so they wind up pushed back to the p-side while the rejected electrons are pushed back to the n-side.
- The charges move throughout the circuit and generate a current. This current can be used to generate power. Some charge carriers combine with the opposite charges in a process known as recombination. Recombination is not desired in solar cells, but is necessary in other devices, like LEDs, to produce light.