Nanoscale spectroscopy of hybrid perovskite solar cells: resolving the role of humidity on device stability through in situ microscopy

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Abstract:Nontechnical: An effective high-efficiency and low-cost photovoltaic technology is still required to successfully replace fossil fuel-based technologies in the US. Currently, only 1% of the total US electricity is generated by solar power. The main challenge for the widespread implementation of solar cells as a source of electricity is the current high cost/Watt. Hybrid perovskites are a very promising new material for manufacturing low-cost photovoltaic modules, but improvement in device stability is essential so that this emerging material can be effectively employed as a photovoltaic technology. In particular, it is unknown how the device performance changes when the perovskite, composed by micron-scale grains, is exposed to humidity. To advance the understanding of how the grains' electrical properties are changing while the solar cells are under operation (and exposed to humidity), this project will implement a novel microscopy technique to resolve, in real-time, the changes that take place within the grains forming the perovskites. These "nanoscale photographs" of the electrical response of the perovskites will be used to determine which physical and chemical processes should be avoided for the realization of stable devices. The integrated educational component of this project focuses on incorporating the research findings into two existing courses in Materials Science and Engineering at the University of Maryland, mentoring undergraduate and graduate students, and broadcasting the scientific results through the LeiteLab YouTube Channel in different languages for worldwide dissemination. Technical description of the project: Hybrid organic/inorganic perovskites based on methyl-ammonium lead iodide are an emerging material with true potential for being a high performance and low cost photovoltaic technology. However, despite the remarkable progress over the last few years, there is still a lack in understanding of why and how the material is changing/degrading when exposed to humidity. The goal of this research is to elucidate the role of humidity in perovskite solar cells by measuring in real-time, with nanoscale resolution, the changes that take place when the perovskite material degrades. By implementing fast illuminated-Kelvin probe force microscopy the Leite group will map the photo-generated voltage in 16 seconds; thus, capturing in real-time the material changes while the device is in operando. This project builds upon the PI's expertise in nanoscale metrologies to image the functionality of devices for energy harvesting and storage. Controlling the negative effect of humidity on perovskites will enable the wide implementation of this material as a reliable and low cost photovoltaic technology.