Precursor impurity control for stable perovskite tandem photovoltaic modules

Halide perovskites are a very promising technology to offer higher-power photovoltaics at low cost. Solar cells based on perovskites with >33% power conversion efficiency have already been demonstrated, which would provide a higher power-to-weight ratio than conventional Silicon panels at similar costs. Such panels would fulfill a critical need from the US Army for power generation in portable or easily deployable arrays that will function under a range of environments.Ā However, their operational stability is still considered to be lacking as compared to incumbent solar technologies, hindering commercialization. Here, we propose that a key route to enabling reliable long-term perovskite stability is by controlling the purity of the perovskite precursor materials. Precursors with different specified purity or from different suppliers are likely to contain different and varying levels of impurity species. We have found that in order to attain high levels of performance and stability, there is a narrow window for the perovskite composition. It has been shown that some precursor impurities can be detrimental to initial device performance, and preliminary data suggests they can also impact long-term stability. Precursor purity also strongly affects cost, so understanding purity requirements and the effects of impurities on stability will be critical to achieving both the technical stability performance and the price points relevant to commercialization.Ā In this project we bring together expertise in material characterization (UCSD) and perovskite device fabrication (Swift). We will carry out a thorough scientific study to establish the presence and nature of impurities in a range of common perovskite precursors. By screening device degradation with accelerated aging methods, we will identify the role of different impurities in device stability. We will use combined experimental and modeling approaches to identify the precursor purity levels needed for devices to attain lifetimes of >4000h at 1sun, 40C, 85% RH, and fabricate perovskite-silicon tandem minimodules that hit this target.