What is the approximate open-circuit voltage produced by a fully illuminated silicon photovoltaic cell?

A single silicon photovoltaic cell inherently produces an open-circuit voltage of about 0.5 volts when fully illuminated. This voltage is determined by the physical properties of the silicon semiconductor material and its bandgap, regardless of how large or small the physical cell is. Because 0.5 volts is quite low, practical solar panels wire many of these individual cells together in series to achieve usable voltages, such as 12 to 18 volts for charging batteries or running equipment. Many students mistakenly choose 0.7 volts because that is the standard forward voltage drop of a silicon diode. While solar cells are effectively large P-N junctions, their open-circuit generating voltage under illumination peaks around 0.5 volts, which makes it the correct exam answer.