Depth profiling fullerene-free organic solar cell blends using neutron reflectivity

In Sheffield, 9% efficient organic solar cells have been made using a new non-fullerene acceptor called ITIC, when blended with semiconducting polymers. GIWAXS measurements have shown that processing conditions such as choice of casting solvent and annealing conditions significantly change the horizontal morphology of the blend films. We expect these processing conditions to influence the vertical structure too as this has been seen for more well-studied systems. The vertical composition of the blend film is known to play a crucial role in the resulting device performance. Neutron reflectivity is therefore essential to probe the vertical structure, providing information inaccessible through other experiments. Together with our accepted SANS beam time we will gain a well-rounded picture, allowing us to understand the importance of processing-morphology-device performance relationships.