The potential barrier in the PN junction is the barrier which does not allow charge flow across the junction normally. This barrier is created by the charge Present in the space charge region. When a P-type Material is brought in contact to an n-type material charge flow across the junction takes place due to the concentration gradient between the two size. After some time the immobile ions are created near the contact which creates an electric field which opposes the flow of current. This Resistance to the flow of charge is known as barrier potential.