Solar Simulator for Multijunction Solar Cells
For series connected multijunction cells, at a given spectrum (e.g. AM 1.5 or AM 0 for space solar cells), one of the cells will limit the current in the series connection of cells. All solar simulators deviate from the true AM 1.5 spectrum, and they are only classified in wide spectral bands (100nm width). So even for class A or A+ solar simulators, it can easily happen that the bandgaps of the multijunction cells are such distributed that the 'wrong' cell will limit the current, if a solar simulator with fixed spectrum is used. In the 70s and 80s, when these measurements were first developed, intercomparisons showed deviations of cell efficiency in fixed spectrum solar simulators of more than 40%.
