An N-type layer is a region of semiconductor, often silicon, doped with atoms that provide extra mobile electrons. These electrons act as negative charge carriers. In a silicon solar cell, the N-type region is paired with P-type silicon, which has an abundance of positively behaving holes.
The boundary between the two regions forms a junction that helps separate light-generated electrons and holes, enabling current to flow through an external circuit. N-type layers also appear in other semiconductor devices, where their carrier properties are carefully controlled during fabrication. Their doping level, thickness, and uniformity affect device performance, so manufacturing requires precise process control.