Dynamics of multicomponent mixtures such as polymer blends are typically studied with QENS and deuterium labelling. Difficulties arise in the data analysis if the coherent signal of the ‘hidden’ component is of the same order of magnitude as the incoherent signal of the component of interest – contamination with the structure factor and any coherent inelastic scattering, means that the self-intermediate scattering function becomes difficult to isolate. One such case are blends of P3HT/PCBM for use in solar cells. They promise low manufacturing costs, high production throughput and large area applications, however efficiencies are still limited to ~ 11%. This study of the dynamics will help to maximise transport within the solar cells, and the use of neutron polarisation analysis to separate the incoherent and coherent scattering will allow unambiguous determination of the QENS signal.