Figure 5: Histogram of the deviation from the average photogeneration in the inhomogeneity map shown in Fig.4 (+/- 0.4% inhomogeneity case). In our data set, the photogeneration deviations for each category are a single value (the value shown on the horizontal axis), and not a continuous spread.
It can be seen from Fig. 4 that the average values, and also the minimum and maximum values of the three strings, are very similar. It can therefore be expected that the bypass diodes will have only a minor effect on the I -V curves, which is also what we found in our simulations. However, in an inhomogeneity scenario, individual cells will be forced into reverse bias along the lower voltage range of theI -V curves, also in the presence of bypass diodes. We therefore have to consider the reverse-bias characteristics of the individual cells when exploring the effects ofI PH inhomogeneity.
Clement et al . [8] published reverse-bias characteristics for different solar cell technologies, and Fig. 6 shows as curve in red (case 1, labelled “IBC homojunction”) a digitized version of the reverse bias characteristics published by Clement et al . for IBC cells.
Case 3, the black curve in Fig. 4 is the simplest case, using for forward and reverse characteristics the sameR Shunt resistance (see also Table I with the standard parameter set used in this study).
The blue curve, i.e. case 2, uses also the sameR Shunt in forward and reverse characteristics, but in combination with an added “softened break-through” compared to the “IBC homojunction” of case 1. This break-through