Poly-crystalline solar panels are also made from silicon. However, instead of using a single crystal of silicon, manufacturers melt many fragments of silicon together to form the wafers for the panel. 

Poly-crystalline solar panels are also referred to as "multi-crystalline," or many-crystal silicon. 

Because there are many crystals in each cell, there is to less freedom for the electrons to move. 

As a result, poly-crystalline solar panels have lower efficiency ratings than mono-crystalline panels.