Characterization of solar cells using electroluminescence and photoluminescence hyperspectral images

We analyze photoluminescence (PL) and electroluminescence (EL) of a GaAs solar cell using a hyperspectral imager that records spectrally resolved images. Thanks to the absolute calibration of the setup, we first investigate the reciprocity relations between solar cells and light-emitting diode and determine the external quantum efficiency from EL images. Spatial variations are observed due to series resistance effect that we can evaluate. Second, the PL experiment allows us to plot the recombination current at a given spatial location versus the quasi-Fermi level splitting at the same location. Under reasonable assumptions, this can be linked to the classical measurement of the short circuit current versus the open circuit voltage. Therefore we perform a contactless mapping of optoelectronic properties such as the saturation currents. The assumptions made in these experiments are discussed in order to correctly investigate polycrystalline solar cells in the future where strong lateral variations exist.