In this paper, two cocrystals 1 and 2 with the same chemical composition [L1.L2 ] (L1 = bis(4΄-pyridyl)-TTF, L2 = 4,4΄-diiodophenyl) were synthesized by slow diffusion with different solvent systems.  Cocrystals 1 and 2 were characterized by single-crystal X-ray and the purity of these two cocrystals was confirmed by PXRD data. The photocurrent responses of these two cocrystals were also tested. Only cocrystal 1 could generate photocurrent signal when exposed to light. From the crystal structure analysis, the possible reason may come from the different  biphenyl conformations in L2.