Spectral analysis of resonant scattering to quantify phase behavior in organic blends

It is important in organic solar cells to understand how phase behavior and possible non-equilibrium states of device morphology relate to functionality. However, characterization of carbon based electronics can be a challenging endeavor due to low levels of crystallinity, anisotropic molecular structure leading to complex three dimensional morphologies, and low contrast that hamper traditional techniques such as electron microscopy or hard X-ray scattering. Recently, studies utilizing resonant x-rays have shown sensitivity to phase behavior but a quantitative characterization is vital to correlate device performance. Here we demonstrate a multi-domain analysis of spectrally resolved scattering using molecular optical constants to accurately calculate absolute domain volume fraction and composition of a model block co-polymer. Our methods address complex absorption and fluorescence that occur at the carbon edge in order to move current models beyond the Born approximation. Techniques developed have been applied to P3HT -- PCBM solar cells to draw conclusions of device morphology.