Q.The principle in which a solar cell operates

A solar cell (photovoltaic cell) converts light energy directly into electrical energy via the photovoltaic effect -- essentially a large-area p-n junction (a thick p-type silicon base with an ultra-thin n-type layer on top, or vice versa for an n-type cell) that generates its own emf when sunlight falls on it, without any external bias. Absorbed photons create electron-hole pairs near the junction, and the junction's own built-in field separates them, sweeping electrons to the n-side (collected by a front metal-grid contact) and holes to the p-side (collected by a back metal contact); this charge separation develops a potential difference ac …