Question

Without external load, the p-n junction solar cell, when kept in the sun, is reverse biased true or false

Answer 1

In a pn junction, by pure random motion, electrons on the n side will move to the p side and vice versa (particles move from high concentration to low concentration). As a result, a depletion layer, a layer of fixed charge, forms between n and p sides in equilibrium. As a result of the charge separation between positive donor ions and negative acceptor ions an electric field is set up that tends to oppose the diffusion. There is now a balance between majority carriers diffusing through the depletion region and minority carriers being swept through the depletion region by the field. The net current is zero for both holes and electrons.

Answer 2

With low reverse bias voltage, the leakage current in nano-amperes flows for Silicon diodes (micro-amperes for Germanium diodes).

Once the PIV (peak -inverse-voltage) of the diode is exceeded, avalanche breakdown will cause current to increase uncontrolled and will damage the diode.