solar cell

Did You Know? How can light make electricity? By exciting electrons to break free from their atoms. A solar cell has an upper layer of negatively charged silicon, with free-flowing electrons, and a lower layer of positively charged silicon, with atoms that are missing some electrons. The placing of these two charged layers next to each other creates a weak electric field. When light penetrates the solar cell and reaches the positively charged layer, its energy is absorbed by some of the electrons which, in their extra-excited state, break away from their atoms. The electric field along the surface where the two layers meet then pushes these electrons into the negative layer. Meanwhile, other electrons in the positive layer move upward into the space the first electrons left behind. In the negatively charged silicon layer, the electrons pile up, increasing the electric charge. When the two layers of a solar cell are connected to a circuit, the electrons flow out of the negative layer through the circuit and back to the positive layer, where they are attracted by the spaces left by the missing electrons. Along the way, the electrons power the inner workings of devices like calculators and spacecraft.