The disclosure provides a solar cell and a back contact structure thereof, a photovoltaic module, and a photovoltaic system. The back contact structure includes a first doped region having an opposite polarity to a silicon substrate and a second doped region having a same polarity as the silicon substrate. An isolation region is arranged between the first doped region and the second doped region. The protective region arranged on the first doped region includes an insulation layer and a third doped layer having a same polarity as the second doped region. An opening is provided in the protective region to connect the first conductive layer to the first doped region. In the present invention, scratches caused by belt transmission in an existing cell fabrication process is resolved.