Quantitative evaluation of inhomogeneous device operation in thin film solar cells by luminescence imaging

摘要

We present a method for quantitative evaluation of electroluminescence images from thin film solar cells. The method called "quantitative electroluminescence imaging" (QuELI) is based on decoupling local equivalent circuit parameters and allows calculation of the local current-density as well as the local series resistance and saturation current-density. By application of this method to electroluminescence images obtained from polymer-fullerene based solar cells, we show that QuELI allows efficient separation between: (a) properties of the electrodes and their associated interfaces by the local series resistance and (b) properties of the active layer by the saturation current-density. We furthermore reveal large scale lateral phase separation via the strong variation in the saturation current-density, which delivers information on the energetic difference of thermal activation of charge carriers across the effective active band gap.