As shown in the picture below, the basic unit of a solar panel (or PV module) is a solar cell, a group of solar cells connected electronically and grouped into a frame to form a panel. Many modules are put together to form a solar array and many PV arrays connected together to form a solar power system.
Solar cell, or photovoltaic cell, which consists of two layers of silicon-based semiconductor wafers. When struck by the photons in sunlight, electrons in the silicon wafers are activated and knocked loose. This is called the “photovoltaic effect”. Solar cells are made of semiconductors such as silicon, which absorb the sunlight and convert it into electricity.
There are off-grid solar systems and grid-connected PV systems. What makes them different is that in the first kind of system the solar energy is stored in batteries bank for personal use, while in a grid-connected solar system you can sell your surplus of electricity back to the grid.
Solar panels not only work on sunny days, solar panels also produce a considerable amount of electricity on cloudy days and during the winter season. So it can generate energy throughout the year.