The temperature 7 of the electrons and holes in the absorber can be found very easily from the magnitude of the emitted energy current. In contrast to the interaction with phonons, where at open-circuit the emitted photon current is equal to the absorbed photon current, for impact ionization at open-circuit the emitted energy current must be equal to the absorbed energy current, since by impact ionization/Auger recombination the electron-hole system does not lose energy. The chemical potential of the emitted photons is then py = t~[c + T]h = 0, and we can calculate the temperature 7д of the electrons and holes by using Planck’s Law in Eq. (2.32) for the emitted energy current. For maximum concentration of the incident solar radiation we find, of course, 7a = 7s at open circuit.