Photoinduced electron transfer in solid films of porphyrin-fullerene dyads was studied using femtosecond pump-probe method. The relaxation of the main photo-product, intramolecular exciplex, was found to be essentially non-exponential. To analyze the decays a model accounting for a distribution of the free or reorganization energies is proposed. The model allows to fit the experimental data using three parameters: non-disturbed time constant, τ0, width of the energy distribution, ΔE, and sensitivity parameter, a = -(Δ G0 + λ0)/2λ0, where ΔG0 and λ0 are the average free and reorganization energies, respectively. The parameters were found to be τ0 = 50 ps, ΔE = 0.09 eV and a = 2 for the exciplex relaxation.