Organic solar cells with conjugated polymers in the active layer are reaching efficiencies and lifetimes compatible with market requirements. Nevertheless, some fundamental aspects about the correlation between molecular structure and dynamics of the polymers and the stability and electrical parameters of the solar cells are still far from a complete understanding.
Neutron scattering experiments performed on thin films and full solar cells with conjugated polymers such as P3HT or P3OT will be presented; in particular, small angle neutron scattering (SANS) to study the polymers in solution, quasielastic scattering (QENS) to study the bulk dynamics of the macromolecules at different temperatures and neutron reflectometry (NR) to study the evolution of the vertical segregation of PCBM in the active layer of P3HT:PCBM solar cells will be discussed.