Solid-state µ-MAS and thin-film NMR spectroscopy on hybrid organic/inorganic perovskite photovoltaic materials

混合有机/无机卤化铅钙钛矿（APbX3）在过去十年中引起了人们的极大兴趣，因为它们可能作为传统硅太阳能电池的替代品，具有优异的功率转换效率，目前高达23%。由于结构灵活，可获得宽带宽的化学成分，包括混合阳离子和/或混合卤化物体系。此外，一系列不同的钙钛矿的合成策略和处理是可能的，除了化学成分影响钙钛矿材料的形态，粒度和晶体缺陷。这些不同层次的结构变化通常会对所得到的薄膜钙钛矿的光电特性产生相互关联的影响，钙钛矿是太阳能电池应用中使用的材料几何形状。与巨大的参数空间相比，系统的研究很少，并且基本上缺少太阳能电池的原位工作条件，即照明。然而，原子分辨率的综合研究对于推导结构-性质关系至关重要，以指导未来的合成策略和高效卤化铅钙钛矿的最佳化学成分。因此，研究计划致力于在薄膜几何形状的混合混合有机/无机卤化铅钙钛矿中弥补这一差距。为此，我们选择了核磁共振晶体学方法，因为它提供了关于原子水平局部环境的补充信息以及远程顺序，因此代表了系统结构研究的最佳方法。基于微线圈设计的新型薄膜MAS NMR探头的开发和实现将允许直接测量薄膜几何形状。此外，光源将安装在大块和薄膜MAS NMR探针中，以便在照明时原位监测多种钙钛矿成分和形态的结构行为。我们期望解决点缺陷、阳离子或卤化物有序/无序以及光照射下结构响应对光电性能的影响等关键问题，从而获得一套高性能光伏钙钛矿材料。体积样品和薄膜几何形状的结果比较将提供合成和结晶条件影响的见解。总体而言，在实际设备工作条件下获得的关于高性能钙钛矿材料的结构见解将最终指向重要的结构-性能关系，以指导钙钛矿材料在太阳能电池设备中的应用。

Hybrid organic/inorganic lead halide perovskites (APbX3) have attracted great interest in the last decade due to their possible application as an alternative to conventional silicon solar cells, with excellent power conversion efficiencies of currently up to 23 %. Due to the flexible structure a wide bandwidth of chemical compositions including mixed cation and/or mixed halide systems are accessible. Furthermore, a series of different synthesis strategies and treatment of the resulting perovskites are possible, that besides chemical compositions impact on e.g. the morphology, particle size and crystallographic defects of the perovskite materials. These structural changes at varying levels often cause interlinked effects on the optoelectronic properties of the resulting thin film perovskites, the materials geometry that is used in solar cell applications. Systematic studies are rare compared to the enormous parameter space, and are essentially missing for in situ working conditions of solar cells, i.e. upon illumination. However, comprehensive studies at atomic resolution are essential to derive structure-property relations in order to guide future synthesis strategies and optimal chemical compositions for high efficiencies of lead halide perovskites. The research proposal, therefore, is dedicated to the closure of this gap for a suit of mixed hybrid organic/inorganic lead halide perovskites in thin film geometries. For this purpose we choose the NMR crystallographic approach as it provides complementary information about the local environment at atomic level in addition to long-range order, and thus represents the optimal methodology for systematic structural studies. The development and implementation of a novel thin film MAS NMR probehead based on microcoil designs will allow for direct measurements of thin film geometries. Furthermore, light sources will be installed in both, bulk and thin film MAS NMR probes, in order to allow for monitoring the structural behaviour of multiple perovskite compositions and morphologies in situ upon illumination. We expect that the key issues, how point defects, cation or halide order/disorder, as well as the structural response upon light irradiation impact on the optoelectronic properties will be answered for a suit of high-performance photovoltaic perovskite materials. The comparison of the results for both bulk samples and thin film geometries will provide insights in the influence of syntheses and thus crystallization conditions.Overall, the achieved structural insights about high-performance perovskite materials under actual device working conditions will eventually point to important structure-property relations to guide future tailoring of perovskite materials with respect to their application in solar cell devices.