Increasing the energy yield of CPV modules through optimized solar cell interconnection

In this paper, solar cell interconnection schemes within FLATCON® CPV modules are investigated in the context of the deviations in current generation between the individual triple-junction cells. For that reason a temperature dependent SPICE network model is developed. A broad parameter identification was carried out. The dark saturation currents of the three subcells are derived from dark IV measurements performed at various temperatures on top and middle component cells as well as lattice matched triple-junction cells. The dependency of short circuit current on temperature was measured with a flash simulator. The ratio of current generation of middle to top cell is calculated with EQE measured at different temperature and the spectrum of the flash simulator as well as the spectrum AM1.5d ASTM. Furthermore, a validation of the developed network model is shown. A good agreement between measurement and simulation is presented for different interconnection schemes. As an application of the model, randomly normal distributed deviations in current generation between the cells within a module are used to determine the difference in mean power output of interconnection schemes. A standard deviation in current generation of 5% leads to a 5% lower mean power output if all cells are connected in series compared to the case that all cells are connected in parallel.