The elucidation of the compositional profile inside the polymer nanoparticles is of critical importance for applications such as water processable organic solar cells. In order to have efficient charge separation and transfer, a nanoscale morphology is needed. This is crucial as charge migration only occurs on length scales up to 10 nm, and if separation is larger than this a large amount of charge recombination occurs, which has a substantial negative effect on overall photovoltaic performance. Therefore, to prevent this loss in optoelectronic performance it is important to design and fabricate nanoparticles with a blended interpenetrating nanoscale structure rather than a separated core-shell structure. SANS would be able to confirm which nanoparticle fabrication methods and blends of materials give the most favourable internal structures and best performances for these applications.