The impact of electrodes and active layer thickness on the current-voltage characteristics of Au/Pentacene/Al structure was studied using a physicallybased 2-D simulation by solving Poisson's, continuity, and drift diffusion equations. The main parameters required for simulation are extracted from the logarithmic representation of experimental current-voltage curves. The simulation results produce an excellent overlapping with the experimental data after including parameters previously found in our model. Finally, the simulation was used to better understand the physical processes together with mechanisms governing the efficiency of the device under investigation and to have a predictive behavior.