How Do Solar Panels Work?

A solar panel consists of many photovoltaic cells, each a sandwich of two silicon layers with different electrical properties. The top layer is "doped" with phosphorus (adding extra electrons, creating n-type silicon), and the bottom layer with boron (creating "holes" or electron gaps, p-type silicon). Where they meet, a built-in electric field forms at the p-n junction. When a photon hits the cell with enough energy, it knocks an electron free, and the junction electric field pushes the electron in one direction, creating a flow of electrical current. Metal contacts on the cell collect and channel this current. A single cell produces about 0.5 volts; cells are wired in series to produce useful voltages (typically 30-40 V per panel). Modern commercial panels achieve 20-23% efficiency, while laboratory cells have exceeded 47%. The cost of solar electricity has dropped 90% since 2010, making it the cheapest source of new electricity generation in most of the world.