A solar panel is a flat construction resembling a window, built with technology that allows it to passively harvest the heat of the sun or create electricity from its energy through photovoltaics.
Passive solar panels include those used to heat water for home heating and to provide hot water on tap. Most commonly, photovoltaics are assumed when speaking of solar panels. Photovoltaic solar panels use positively- and negatively-doped silicon working in conjunction with conductors on the alternately-charged surfaces. Electricity is created when photons strike the surface and excite electrons to the point that they leave their valence.
Solar panels are increasingly in popularity as solar power has reached price parity with oil and, simultaneously, more and more jurisdictions mandate the use of solar panels or other renewable energy sources in construction of new buildings.