Photoinduced charge separation is the process of an electron in an atom or molecule, being excited to a higher energy level by the absorption of a photon and then leaving the atom or molecule to free space, or to a nearby electron acceptor.
[1] An atom consists of a positively-charged nucleus surrounded by bound electrons.
The nucleus consists of uncharged neutrons and positively charged protons.
An electron which is stationary and completely free from the atom has an energy of 0 joules (or 0 electronvolts).
The electron will reside in this energy level under normal circumstances, unless the ground state is full, in which case additional electrons will reside in higher energy states.