We propose to study a range of new lower energy gap organic photovoltaic (OPV) materials deposited by spray coating using neutron reflectivity. The new materials to be studied will have low energy gaps and therefore utilize a greater range of the available solar spectrum and make higher power conversion efficiency devices. We will use an innovative spray coating process, which will allow a much greater degree of control over the nano-structure of the blended OPV active layer in our samples. We propose to use neutron reflectivity to measure the composition depth profile of our new materials deposited by a novel spray coat technique. This will determine the extent to which we can control of the composition depth profile and therefore achieve better devices. This research will be a crucial component in a broader project to develop superior materials and a scalable route to production.