The Sun gives off 1,000 watts of energy per square meter of the Earth’s surface, which, if we could harness all of it, is more than enough to fulfill all of the world’s current electricity needs. It’s not easy to do this, however, which is why we still rely primarily on other energy sources. A solar cell, or photovoltaic cell, harnesses energy from photons of sunlight by having them excite electrons in a material. An electric field is established within the solar cell using a process called doping, and this makes it so that the excited electrons can only flow in one direction. Thus, when sunlight strikes the solar cell, a current flows, and this is the basic principle on which solar cells operate to capture energy. The harnessed energy can either be used immediately or it can be stored for later use. Designing more efficient solar cells is a very active area of research, and you can expect their efficiency to continue to increase in coming years.