Question

what the principle behind the daiode

Answer 1

Main functions. The most common function of a diodeis to allow an electric current to pass in one direction (called the diode's forward direction), while blocking it in the opposite direction (the reverse direction).

Answer 2

It is called as "barrier potential" because it acts as a barrier and opposes the flow of positive and negative ions across the junction. To make use of this p-n junction diode we have to apply an external DC voltage to it. ... This is the working principle of diode