Solar Cell
Definition
A device that converts sunlight directly into electricity using the photovoltaic effect in semiconductors.
Technical definition
A large-area p-n junction (usually silicon) where absorbed photons with energy above the band gap create electron-hole pairs, separated by the junction's built-in field to drive current. Typical efficiency 20–26%; theoretical (Shockley-Queisser) limit ~33% for single junctions.
Example
A rooftop panel (~20% efficient) turns one-fifth of sunlight into electricity — the rest becomes heat or reflects away.
Common confusion
Solar cells do not store energy — they only convert it while illuminated. Nighttime power needs batteries or the grid; the panel itself is a generator, not a battery.