Ion Migration in Lead Halide Perovskite Solar Cells

As our world faces climate crisis, there is a global need for cheap and efficient solar cell technologies. Perovskite solar cells have emerged as an exciting technology, combining both these aspects of high energy conversion efficiency together with cheap fabrication methods. They would be outstanding if not for the one issue of their instability: nowadays they are unfortunately still too unstable for commercial applications in the photovoltaic sector. One of the reasons behind this instability is the ion migration process taking place in these cells, where ions from the ABX3 perovskite crystal structure start to migrate within the devices. The research question driving this thesis is the following: "How can we reduce ion migration in lead halide perovskite solar cells?" To answer this question, we use an electric spectroscopy technique, Transient Ion Drift (TID), to measure the ion migration dynamics in a variety of perovskite cells. This powerful technique can quantify key parameters in the ion migration process, such as the activation energy for ion migration and the density of mobile ions. We vary the perovskite composition, morphology and interface layer, and find interesting pathways towards more stable perovskite solar cells exhibiting reduced ion migration.