While PV power systems are elegant in their simplicity, the material science behind module technologies and manufacturing is considerably more complex. Today, you do not need to be a rocket scientist to design and install high-quality PV power systems. In the 1960s and 1970s, however, most of the scientists and researchers who discovered techniques for improving c-Si PV cell performance were working with rocket scientists to improve the performance of satellites. This glossary defines some of the technical terms I use throughout this article to describe c-Si PV cell technologies and module construction.
Base layer: The silicon substrate, the foundation for the layers that form a solar cell.
Carriers: Light-generated carriers are either electrons or holes (missing electrons) in a solar cell’s atomic structure.
Dopants: Impurities that have a net negative or positive charge as compared to silicon. The most common dopants used in modern c-Si solar cells are phosphorus and boron.
Doping: The technique of intentionally adding a concentration of impurities to a semiconductor material to vary the electric charge.
Electron: A negatively charged subatomic particle. An electron can be either free, meaning not attached to any atom, or bound to the nucleus of an atom.
Electron-hole pair: Incident light that impacts a solar cell with sufficient energy will dislodge an electron from its bond in the crystalline structure and thereby create a hole. The negatively charged electron and positively charged hole are a pair of carriers that provide the basic constituents for electric current flow in the solar circuit.
Emitter layer: The layer of a c-Si cell that is exposed to sunlight. The emitter layer absorbs incident photons and emits charged particles known as carriers.
Fingers: Metallic contacts that are typically screen-printed on the front surface of a c-Si cell.
Hole: An empty space in an atom’s structure for an electron to fill. For simplicity, often the hole is visualized as a positively charged particle that can move through the crystal structure.
Lifetime (of a carrier): The length of time that a free-moving carrier can exist in the solar cell structure before it is reabsorbed.
Light-generated carriers: Either electrons or holes, which are essentially missing electrons, in a solar cell’s atomic structure.
Majority carrier: A carrier that has a similar charge compared to the surrounding material, such as electrons in n-type material and holes in p-type material.
Minority carrier: A carrier that has an opposite charge compared to the surrounding material, such as electrons in p-type material and holes in n-type material.
N-type silicon: Silicon doped with an impurity that results in a net negative charge when compared to pure silicon. Negatively charged silicon is typically doped with phosphorous.
P-type silicon: Silicon doped with an impurity that results in a net positive charge when compared to pure silicon. Positively charged silicon is typically doped with boron.
Photoelectric effect: The release of electrons from certain metals and semiconductors in response to light.
Photons: Packets or particles of energy contained in electromagnetic radiation, which includes the visible light spectrum.
P-N junction: The intersection of the base layer and the oppositely charged emitter