Collaborative Proposal: Multidimensional Tracking of Local Environment-Affected Transport Pathways in Perovskite Solar Cells

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Organic metal halide perovskites have gained enormous research interest as materials for solar cells, and their efficiencies are now approaching those of conventional silicon devices. Additionally, they allow for more scalable fabrication and for the development of higher efficiency tandem devices with two different absorbers. Perovskites have a complicated crystal structure with many forms of disorder. Despite this complexity, they have a robust ability to transport charges without losses that reduce efficiency. However, fundamental questions regarding the role of the disorder and its effect on the generated photocurrent remain unanswered. This project uses advanced, ultrafast spectroscopy to measure the effects of disorder on energy and charge carrier flow in perovskites. These results are directly coupled to the subsequent device behavior. Overall, this project provides an understanding of the fundamental physics of the materials while also providing guidance on practical methods to improving device efficiencies. The principal investigators will use this research topic to engage with K-12 students, undergraduate students, and community college teachers in research. They will also reach out to the general public through public lectures, hands-on presentations at a local amusement park, and online classes.The objective of the project is to measure the effect of spatial irregularity from defects and mobile cations on exciton and free carrier transport in perovskite thin-film photovoltaic materials and devices. Multidimensional coherent spectroscopy experiments will be performed in a tight feedback loop with controlled and scalable synthesis enabling new understanding of microscopic carrier transport to spark transformative gains in device efficiency. Experiments are performed on perovskite materials and photovoltaic devices in order to: 1.) quantify the effect of defect density on carrier transport and dynamics through a novel implementation of multidimensional coherent spectroscopy; 2.) measure the effect of both static and dynamic cation disorder on carrier lifetime; 3.) optimize material composition and device architecture through close coupling between optical experiments and device fabrication; and 4.) characterize scalable deposition techniques and their effect on film heterogeneity at varying size scales. As part of the work, new experimental approaches are developed, including a) simultaneous detection of photoluminescence and photocurrent through multidimensional spectroscopy and b) energy-coupled deposition of the perovskite materials to yield improved film quality for scalable device fabrication.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.