Question

what is p-n junction.?? explain.

Answer 1

A p–n junction is a  interface between two types of semiconductor materials, p-type and n-type. The "p" (positive) side contains an excess of holes, while the "n" (negative) side contains an excess of electrons in the outer shells of the electrically neutral atoms . This allows electrical current to pass through the junction only in one direction. The p-n junction is created by doping.  this doping would introduce a grain boundary between the semiconductors that would severely inhibit its utility by scattering the electrons and holes.
p–n junctions are elementary "building blocks" of semiconductor electronic devices such as diodes, transistors, solar cells, LEDs, and integrated circuits.