Simulations using SPICE

We prepare an electrical network simulation as already used in Section 5.3 to further analyze if the independent diode model used in the LIA approach holds. We focus on a monocrystalline solar cell, which suffers from a high local series resistance due to a broken finger. For the simulation, we cut the finger at a specific distance from the busbar. By varying this distance, the solar cell suffers globally and locally from different series resistance values. Table 5.2 summarizes all parameters inserted into the simulation.

The simulation is carried out for different applied voltages and illumina­tion intensities to obtain the light-IVand the Jsc – Voc characteristics. At the maximum power point, we extract a series resistance image (Rs-SPICE) as it would be extracted from a luminescence image using the approach of Trupke et al. (2007). Other local and global parameters needed for the LIA approach are determined as explained in the previous section.

Figure 5.28 shows the results of this simulation. The x-axis gives the energy conversion efficiency, which is directly obtained from the SPICE light-IV curve, and the y-axis represents the value obtained by the LIA approach using the Rs-SPICE image. Deviations below 1.5%rel indicate that both methods are in good agreement for the analyzed range of series resistances.

Figure 5.29 shows for the highest global series resistance value (Rser, FF = 2.3 O cm2) the light-IV curves and in the inset the shifted light – IV curve in a logarithmic scaling. It can be seen that the LIA approach using the Rs-SPICE image is in good agreement with the light-IV curve directly obtained with SPICE. Note that the global one or two-diode model is not able to reproduce the recombination properties and would thus lead to wrong conclusions.

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Figure 5.28 Simulation carried out with SPICE to demonstrate the LIA approach. The x-axis gives the efficiency obtained directly from the SPICE-/V curve and the y-axis, the efficiencies calculated with the LIA approach using the Rs-SPICE image.

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Figure 5.29 Light-/V curves of a symmetry element obtained directly from SPICE and from the LIA approach using the Rs-SPICE image. The inset shows the data around the maximum power point in a logarithmic scaling.

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Figure 5.30 Comparison of efficiencies obtained from the light-/Vcharacteristics to effi­ciencies obtained from LIA using a measured series resistance image. The data shown with a blue square corresponds to the industrial screen-printed solar cell of Table 5.3 and Figure 5.27.

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