A solar cell (photovoltaic cell) is essentially a p-n junction that converts light energy directly into electrical energy.

• Use of no external battery: Unlike a photodiode, which needs a battery to function, a solar cell generates its own voltage (Electromotive Force, EMF).
• When light hits the junction, carriers are generated and separated by the built-in field. This creates a potential difference across the terminals, allowing it to drive current through an external load. It effectively acts as a power source.