The influence of module design on the performance of OPV modules was studied, especially longitudinal partition effects. Two different module designs were used, one with wider cells (8 mm) and one with narrower cells(3.7 mm).The narrow structure had a current extraction metal sub-electrode in the middle of the module, and a tandem series connection of 4 or 5 cells was used for a fixed total module area. The current density, fill factor, shunt resistance, and power conversion efficiency of the narrow cells were higher than those of the wide cells with a comparable length-to-width ratio. As the longitudinal partitioning of a cell increases, the performance of the device increases. However, the effective active area of the module decreases, so the total power output will decrease. The optimum length-to-width ratio of wide or narrow cells is between 16 and 18. (C) 2013 Elsevier B.V. All rights reserved.