Figure 4: Inhomogeneity map [in “% of average”] of the
photogeneration J PH used for the simulation of
modules with I SC-mismatched cells. The 6 x 10
distribution in the upper schematic is taken from a subset of the
intensity data map of the paper of Ramspeck [6]. The lower schematic
lists minimum, average and maximum photogeneration in the cells of the
three different cell strings in the module, and it additionally serves
as color scale for upper schematic with the +/- 0.4% inhomogeneity case
shown here.
In case of completely identical cells in the module, the illumination
intensity map in Fig. 4 translates directly into an identicalI PH photogeneration map. It therefore describes
the best expectable I SC inhomogeneity
distribution, limited only by the illumination inhomogeneity of a
state-of-the-art module flash tester.
We will also explore the effect of larger inhomogeneities, by usingI PH maps that are scaled from the +/- 0.4%
inhomogeneous map of Fig. 4 to inhomogeneities of +/- 1.0% and +/-
2.0%. These larger inhomogeneities can be understood as either
representing measurements with a less ideal module flash tester, or
representing I PH inhomogeneity distributions
originating from a combination of cell production quality variation in
with an illumination area inhomogeneity.
Note that our inhomogeneity map consists of only seven different values,
as is shown in the histogram in Fig. 5 for the +/- 0.4% inhomogeneity
case. Our cases of increased inhomogeneity only spread these seven
values over a larger minimum-to-maximum range. These maps are therefore
only a rough representation of a real-world inhomogeneity distribution
but will serve sufficiently well to show the fundamental effects of
inhomogeneity.