When a photon (a particle of light) hits the solar cell with energy equal to or greater than the band gap, it knocks an electron loose. This creates an electron-hole pair .
The engineering frontier is currently focused on and Tandem Cells . While traditional silicon cells have a theoretical efficiency limit (the Shockley-Queisser limit) of about 33%, layering different materials allows the cell to capture different parts of the light spectrum. Solar Energy: The Physics and Engineering of Ph...
To make these electrons move in a specific direction (creating a current), engineers create a P-N junction. By "doping" silicon with elements like phosphorus (yielding an n-type layer with extra electrons) and boron (yielding a p-type layer with "holes"), an internal electric field is established. This field pushes the excited electrons toward the front of the cell and the holes toward the back. The Engineering: Building an Efficient Cell When a photon (a particle of light) hits
Fine metal "fingers" are printed onto the cell to collect the flowing electrons. The engineering trade-off here is surface area: the grid must be conductive enough to carry current but thin enough not to shade the silicon from the sun. This field pushes the excited electrons toward the
The foundation of solar energy is the , first observed in 1839 by Edmond Becquerel. To understand how it works, we have to look at the subatomic level of semiconductors, usually silicon.