Measuring refractive index profiles within thin-film photovoltaics with high spatial resolution using the modified IM-IWKB method

We derive a correction to the phase contribution for the reconstruction of refractive index profiles within thin-film photovoltaics using the Index Matched Inverse Wentzel-Kramers-Brillouin (IM-IWKB) Method. We quantify the improvement of the refractive-index reconstruction due to this modification for structures typical of organic photovoltaics. Near the low-index surface of the photoactive layer, this modification reduces the fractional error in the reconstructed profile by a factor of ten, resulting in a highly accurate refractive index reconstruction throughout the entire film thickness. This technique is applicable to the reconstruction of the refractive index profiles within any thin-film photovoltaic material.