Relation between luminescence and open-circuit voltage in Cu(In,Ga)Se2 solar cells

We report on comparative electroluminescence and photoluminescence measurements on Cu(In,Ga)Se2 solar cells and demonstrate that the spectral peak value or the integrated luminescence spectrum may not always reflect the photovoltaic “quality” in terms of open-circuit voltage. Spectra from Cu(In,Ga)Se2 samples may have a comparable quasi-Fermi level splitting but a different spectral width or peak height, determined by the different sub-gap absorption properties. It is suggested that a more reliable evaluation of luminescence spectra should also consider the analysis in the high-energy spectral range which reflects the quasi-Fermi level splitting and which is shown to better correlate with the open-circuit voltage.

► Analysis of electroluminescence and photoluminescence with Planck's generalized law
► Identification of source for scattering in data of evaluated luminescence
► Integral or maximum of the spectra is less suitable than high-energy range.
► Improved correlation between luminescence evaluation and open-circuit voltage