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
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. Solar Energy: The Physics and Engineering of Ph...
In a semiconductor, electrons exist in a "valence band" where they are bound to atoms. Above this is the "conduction band." The energy difference between these two is the band gap. To make these electrons move in a specific
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. The Engineering: Building an Efficient Cell Fine metal
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.