The photoelectric effect is the historic origin of the quantum particle description of light. From it we learn that when light is shone onto a metal single photons interact with single electrons in the metal which are ejected if the absorbed energy is larger than the binding energy of the metal.
The (free) process is:
However, this process violates conservation of energy (all final states are real particles). Of course the reason the process occurs is because the electron is initially bound (not free), and some energy goes into releasing the electron from the metal potential.
The question is, is there anyway to do this calculation in QED, somehow incorporating the binding energy in the calculation?