The convolution integral on the right-hand side expresses the probability of recombination for electrons and holes. In the integrand, the joint density of states(JDOS), ρ J (E i , E f ), connects the initial states, at energy E i , and the final states, at E f = E i -hc/λ em , while the (generalized) distribution functions for electrons, f e (E i , T ), and holes,