As we can see the anatomy of the cell, it can be observed that the n-type layer of semiconductor is thin in comparison to the p-type layer of semiconductor. This is to allow the light particles to reach the charged space field or the p-n junction. When light particles or photons hit the charged space field, their energy is absorbed by the electrons. These electrons are now at a higher state of energy. Eventually the threshold energy of charged space field is breached and the electrons and holes move freely.
Now, if an external load is applied to the cell from the terminals via the conducting metal strips and the back plate, the electrons start flowing in the circuit which gives rise to an electrical current (which is in the opposite direction of the electron flow). Due to opposite polarity, the electrons get attracted to the holes and re-enter the circuit via the back plate and return to the state of electrical neutrality.