Deep level transient spectroscopy (DLTS) has been used to detect the contribution of interface-related states, responsible for minority carrier lifetime reduction in C-60/p-Si solar cells. The very low efficiency of C-60 based solar cells is found to be due to the presence of one hole level E-v + 0.70 eV at the interface of C-60/p-Si heterojunction. The hole capture cross-section and the variation with temperature have been determined, to account for minority carrier lifetime of the material. A large barrier for hole capture, implying a large electron-phonon interaction, characterizes the observed hole level. A pronounced reduction in DLTS peak of the dominant level (0.70 eV) due to injection of electrons provides evidence of electron-hole recombination. A detailed characterization indicates that a dominant deep level, with comparable electron and hole emission rates, acts as a recombination center, which governs the minority-carrier lifetime