In many photo-productive systems this charge separation is kinetically isolated by delivery of the electron to a lower energy conductor attached to the p/n junction or into an electron transport chain. In this case some of the energy can be captured to do work. If the electron is not kinetically isolated thermodynamics will take over and the products will react with each other to regenerate the ground state starting material. This process is called recombination and the photon's energy is released as heat.
:Recombination of photoinduced oxidation
:[ML] + donor → [ML] + donor