Muon Spin Relaxation Investigation of 2D/3D Perovskite Solar Cell Materials Containing 5-AVA Cations

Perovskite cells are an exciting new type of third generation photovoltaics. The ‘perovskite’ layer is efficient at absorbing sunlight and only a very small amount of material is needed to make an efficient device. One of the problems of early perovskite solar cells is lack of stability of the soft perovskite material – in particular the presence of mobile ions. These ions can move so easily that they contribute to degradation. This problem is being addressed by using large organic cation additives. There is evidence that cation engineeringsupresses ion motion, which helps explain the improved stability. However, there have been very few direct measurements of ion motion in the newest 2D perovskites. We would like to use muon spectroscopy to measure iodide motion in these 2D/3D materials to prove that cation engineering causes changes to the activation energy for ion motion.