IIn this paper the influence of different parameters such as active layer thickness, light intensity and charge separation distance on the photocurrent-voltage, short circuit current density (J_sc) and open circuit voltage (V_oc ) characteristics in MEH-PPV:PCBM BHJ devices is studied. For this purpose, the numerical continuum model based on drift-diffusion approximation and simulation tool ATLAS-SILVACO package are used. The J-V characteristics of MEH-PPV: PCBM BHJ devices under illumination change considerably with varying the active layer thickness from 40nm to 280nm. In these devices, as the active layer thickness increases from 40 nm to 120 nm the short-circuit current density increases dramatically. The open circuit voltage (V_oc) is partially affected by varying the active layer thickness. In these devices, as the light intensity increases, the current density would increase at low voltages. Also, as the charge separation distance “a” increases, The exciton dissociation rate (k_diss n_exc) and current density would decrease. پرونده مقاله