He shows that the first and the third of these can be expressed as a resistance times the current: I D R 1 . As for the second, the difference between the quasi-Fermi levels at the junction, he says that we can estimate the current flowing through the diode from this difference. He points out that the current at the p terminal is all holes, whereas at the n terminal it is all electrons, and the sum of these two is the constant total current. So the total current is equal to the decrease in hole current from one side of the diode to the other. This decrease is due to an excess of recombination of electron-hole pairs over generation of electron-hole pairs. The rate of recombination is equal to the rate of generation when at equilibrium, that is, when the two quasi-Fermi levels are equal. But when the quasi-Fermi levels are not equal, then the recombination rate is e ( ϕ ϕ p − − ϕ ϕ n ) / V T times the rate of generation. We then assume that most of the excess recombination (or decrease in hole current) takes place in a layer going by one hole diffusion length L p into the n material and one electron diffusion length L n into the p material, and that the difference between the quasi-Fermi levels is constant in this layer at V J . Then we find that the total current, or the drop in hole current, is