Organic solar cells (OPVs) are photovoltaic devices that can convert the energy from sunlight into electricity and have attracted much attention as a viable green energy source for the future. Over the past few years, organic photovoltaics (OPVs) employing non-fullerene, n-type small molecular acceptors have achieved significant progress benefiting from their tunable optical properties and electronic energy levels compared to conventional fullerene acceptor. It is well accepted that the morphology of the photovoltaic blends of OPVs play an important role in determining the OPV performance. Both the nanoscale morphology in the lateral direction and the vertical component distribution (i.e. vertical stratification) in the cross-section of photovoltaic blend films are important. We intent to use NR to explore the compositional depth profile of polymer:nonfullerene systems.