Epitaxially grown tin perovskites

该项目探索外延生长的锡(锡)钙钛矿作为铅(铅)基材料的替代品。重要的是，锡钙钛矿具有窄的带隙，这是单结太阳能电池的理想范围，这也将使全钙钛矿多结太阳能电池成为可能。此外，它们更环保。然而，到目前为止，锡钙钛矿的功率转换效率低于它们的铅同行。需要克服的最关键的障碍之一是Sn2+氧化成Sn4+的趋势。在这里，我们将使用外延生长方法来避免促进化学反应导致锡的氧化的溶剂，我们将从原子水平对这些锡钙钛矿进行表征。具体地说，我们将实验证明锡钙钛矿表面的原子结构，如CH3NH3SnI3，以定位Sn4+缺陷，并了解在钙钛矿太阳能电池中容易发生的界面现象。此外，我们将向表面添加掺杂剂和吸附物，如环境气体分子，以从根本上研究在原子尺度上发生的与性能增强、降解和氧化有关的特定相互作用。为了弥补尺寸差距与应用之间的差距，我们将在微米尺度上使用表面技术来探测大规模的不均匀、晶界、功函数、接触电势差和表面光伏。对器件水平的充分了解需要使用最先进的解决方案工艺作为基准来制造锡基钙钛矿型太阳能电池。然后，我们将应用优化的结构，利用纳米和微观表征的知识以及外延生长的锡钙钛矿吸收材料来制备高效和长期稳定的新型锡基太阳能电池。我们认为，同一类型样品的原子、微观和宏观尺度之间的关联对于深入了解锡钙钛矿将是特别有成效的。

This project explores epitaxially grown tin (Sn) perovskites as alternatives to lead (Pb) based materials. Importantly, Sn perovskites have a narrow bandgap that is in the ideal range for a single-junction solar cell, which will also enable all-perovskite multijunction solar cells. In addition, they are more environmentally friendly. However, so far power conversion efficiencies of Sn perovskites are falling short to their lead counterparts. One of the most critical obstacles to overcome is the tendency of Sn2+ to oxidize to Sn4+. Here, we will employ epitaxial growth methods to avoid solvents that promote chemical reactions leading to oxidation of Sn and we will characterize these Sn perovskites down to the atomic level.Specifically, we will experimentally evidence the atomic structure of Sn perovskite surfaces such as CH3NH3SnI3 to localize Sn4+ defects and understand interface phenomena that readily occur in perovskite solar cells. Furthermore, we will add dopants and adsorbates, such as environmental gas molecules to the surfaces, to fundamentally study the specific interactions that occur on the atomic scale with respect to performance enhancements, degradation, and oxidation. To bridge the size gap to the application, we will use surface techniques on the micrometer scale probing large-scale inhomogeneities, grain boundaries, workfunctions, contact potential differences and surface photovoltages. A full understanding on a device level necessitates the fabrication of Sn-based perovskite solar cells using state of the art solution-processing as a benchmark. Then we will apply the optimized architectures and use the knowledge from the nanoscopic and microscopic characterizations as well as epitaxially grown Sn perovskite absorbers to fabricate novel Sn based solar cells that are highly efficient and long-term stable. We believe that the correlation between atomic, micro- and macroscale on the same type of samples will be particularly fruitful to gain a thorough understanding of Sn perovskites.