How Solar Cell Works

Bohr presented his theory of atomic model in 1913 that is more stable than that of Rutherford theory. According to his theory

Electron with mass (Mc) revolves around the nucleus in an orbit with radius (rn) and angular frequency (ωn). The centrifugal force produces is given by
F = Mc . rn. ωn^2
Electrons are held in an orbit around nucleus of an atom with a coulomb force
F = q 1 q 2 / 4 π ε r^2

These two forces are responsible for the movement of electron in an orbit.

Apart from Bohr's model, there is another theory called Plank's Theorem can be use to help an electron to remain in its orbit. According to this theory, electrons remain in an orbit, where angular momentum is an integral multiple of plank's constant.

An electron in an orbit contains energy given by En = mc * rn^2* ωn^2.

Now to move electron from its orbit to higher orbit, it is necessary to provide energy to that electron greater than that of given in the above equation from outside.