  We present direct measurements of depth-resolved band gap variations of
CuIn(1-x)Ga(x)Se2 thin-film solar cell absorbers. A new measurement technique
combining parallel measurements of local thin-film interference and spectral
photoluminescence was developed for this purpose. We find sample-dependent
correlation parameters between measured band gap depth and composition
profiles, and emphasize the importance of direct measurements. These results
bring a quantitative insight into the electronic properties of the solar cells
and open a new way to analyze parameters that determine the efficiency of solar
cells.
