Micrometric investigation of external quantum efficiency in microcrystalline CuInGa(S,Se)2 solar cells

•We record external quantum efficiency with high spatial and spectral resolution.•Spatial fluctuations of quantum efficiency around the band gap can be studied.•On CuInGa(S,Se)2 absorber we can map minority carrier diffusionlength•The use of a white laser is a major tool to look at local photovoltaic properties.

We present in this paper small scale spatial fluctuations of the spectral response of CuInGa(S,Se)2 polycrystalline solar cell. The experimental method is based on light beam induced current cartographies under different excitation wavelengths. From those measurements we can map minority carrier diffusion length Ln over the cell with a spatial resolution of about 2 μm. Spatial variations of Ln are evidenced, which result in a standard deviation of around 130 nm. The experiment also evidences spatial fluctuations of the external quantum efficiency that can arise from surface recombinations.