Determination of the quality of CuInS2-based solar cells combining Raman and photoluminescence spectroscopy

Raman and photoluminescence spectroscopy are tested for quality assessment of the absorber layers in CuInS2 thin film solar cells. A correlation between the linewidth of the Raman A1-mode and the electrical parameters of the solar cell is found. For linewidths larger than 3.8 cm−1 the solar cell parameters deteriorate significantly. For smaller linewidths the solar cell parameters level off. A similar correlation is found between the solar cell parameters and defect related photoluminescence intensities. Also here a limit intensity can be derived which predicts the performance of the absorber layer in the solar cell. The leveling off or saturation behavior of the solar cell parameters at sub-optimum values indicates that even high quality absorber layers are limited in performance. This performance limit is below the theoretical limit for space charge recombination. Thus other origins of performance limitation than structural defects are present in CuInS2-based devices.