Perovskite materials used in next-generation solar cells and LEDs break down when exposed to air and light, and this project will use nuclear magnetic resonance to watch those chemical reactions happen atom by atom. The problem is that metal halide perovskites are remarkably sensitive to oxygen, humidity, and illumination—they can degrade or transform in ways that are sometimes harmful and sometimes beneficial, but no one knows exactly how. Without atomic-level understanding, researchers cannot rationally design coatings or treatments to stabilise them. PhotoPeroNMR will combine synthetic chemistry with solid-state magic angle spinning NMR to study how perovskite surfaces react with ambient gases, identify the chemical species that form, and—critically—observe structural changes inside intact working devices under illumination. The project covers lead-based and lead-free perovskites and double perovskites. If successful, the work will produce a framework for designing passivation agents that protect these materials. That could make perovskite solar cells and LEDs durable enough for commercial use—lighter, cheaper, and more efficient than current silicon-based alternatives—without relying on trial-and-error approaches.
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The climate emergency makes the search for new more efficient energy materials imperative. Metal halide perovskites (MHPs) belong to a class of materials promising highly efficient, affordable, and lightweight solar cells and light emitting diodes. One of the key challenges is that these materials are remarkably sensitive to ambient conditions and readily undergo chemical transformations in the presence of oxygen, humidity and under illumination. While these processes can be either pernicious or beneficial, very little is known about their atomic- level mechanism, which makes it difficult to rationally design mitigation strategies. PhotoPeroNMR sets out to address this challenge by using a combination of highly efficient synthetic approaches and solid-state Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR). The project will study the reactivity of MHP surfaces with ambient gases, identify the chemistries of the surface species across a wide range of structurally diverse materials relevant to optoelectronics, including lead and lead-free perovskites and double perovskites. Next, it will develop a strategy to access atomic-level (local) structural data from MHPs in their form directly relevant to optoelectronics, intact optoelectronic devices. It will develop a strategy to illuminate MHPs in a variety of atmospheres and study the microscopic mechanism of the resulting transformations. Finally, it will elucidate the local structural changes taking place in devices under illumination using operando NMR. The combined knowledge obtained here will serve to formulate rational design principles enabling the design of passivation agents with improved characteristics. This local structure characterization framework will provide an underpinning microscopic insight into the most successful materials, naturally combining the effects of intentional and unintentional surface passivation, photoinduced effects, and interactions with the neighboring device layers.
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