Figure 4 shows the photovoltaic performance distribution of cells fabricated without using imposed substrate vibration during deposition of PEDOT:PSS films spun at 5000 rpm. Data from 14 cells were used, in which cells 1 to 7 are associated with the first substrate and 8 to 14 are associated with the second substrate. Parameters used to characterize the photovoltaic performance include the short-circuit current density (), open-circuit voltage (), FF, and PCE. The data for cell No. 3 were excluded because this cell was defected with zero . Figure 4(a) shows the distribution plots of and . The values are scattered, among which the minimum is 0 in cell No. 3 (failed and, therefore, was excluded from the plot), while the maximum is in cell No. 5. In addition to the cell No. 3 with zero , three other cells, i.e., cell Nos. 2, 10, and 11, show very low values, indicating current leakage in these cells, perhaps due to the presence of pinholes in at least one layer of those cells and, therefore, a low shunt resistance. Cell Nos. 2 and 3 are on one substrate, whereas cell Nos. 9 and 10 are on the second substrate. It is found that the scattered variation in of cell Nos. 1 to 7 on one substrate is somewhat similar to that of the cell Nos. 8 to 14 fabricated on the second substrate. In contrast, the values of are relatively consistent with negligible variation; the values vary from 409 mV in the cell No. 11 to 462 mV in cell No. 9, if the of the defected cell No. 2 with zero short-circuit current is discarded. The is known to be dependent on the energy level between the donor and the acceptor, which for the chosen polymer solar cell structure varies from 400 to about 600 mV, affected by thermal annealing,3,10–12 and is independent of the thickness of the active layer.8,9 The is independent of the roughness of the film, as well, for instance, for spray-on cells, the of 580 mV has been reported for the cells fabricated at different process parameters.35,36 Thus, the results of Fig. 4(a) showing that the average is around 450 mV, even when the is low due to charge recombination and imperfections in the film structure are reasonable.