Photoinduced electron transfer in solid films of porphyrin-fullerene dyads was studied using ferntosecond 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, tau(0), width of the energy distribution, Delta E, and sensitivity parameter, a = -(A G(0) + lambda(0))/2 lambda(0), where Delta G(0) and are the average free and reorganization energies, respectively. The parameters were found to be tau(0) = 50 ps, Delta E = 0.09 eV and a = 2 for the exciplex relaxation. (c) 2007 Elsevier B.V. All rights reserved.