Perovskite Heterostructure Investigations using Vacuum Evaporation and X-ray diffraction - PHIVE-X

钙钛矿光伏发电近年来发展迅速，光伏效率达到20%以上，接近热力学（Shockley-Queisser）极限。此外，通过巧妙地选择有机阳离子，混合钙钛矿可以直接在二维层状结构中生长，从而形成预先结构的层堆叠。对于这些类型的钙钛矿，即使只在较厚的“3D”薄膜上使用一层薄薄的2D钙钛矿作为屏障，稳定性也会大大提高。在这个项目中，我们计划利用真空蒸发来解决这些材料惊人的物理特性和维度的影响。虽然2d钙钛矿已被证明以自分层方式从溶液中获得，但尚未显示使用高精度真空蒸发技术的2d分层。在PHIVE-X中，我们将利用钙钛矿晶体结构和电性能的可变性来遵循两条主要途径：实现真空沉积，自结构的2D钙钛矿和制造具有不同化学计量的交替钙钛矿的高精度薄膜堆栈-强制2D钙钛矿。后者是唯一可行的使用真空沉积独特的薄膜控制。因此，我们拓宽了可能的材料选择，开辟了一个全新的钙钛矿研究领域。通过在生长过程中精确控制化学计量，材料的变化改变了超薄膜的带隙和折射率。特别是，我们打算以一种全面的方式利用这种方法的机会，比如通过交换碘化物和溴，以及甲基铵和甲脒来调整近0.8 eV的带隙。这两条路径都将应用于器件概念：自结构和强制二维钙钛矿将在太阳能电池和发光器件中实施，并研究其性能和稳定性。使用强制的二维钙钛矿，我们也将有效地形成双异质结构和超晶格。如果调整得当，载流子和光约束为钙钛矿激光器等光电应用创造了一系列机会。结合德累斯顿和<s:1>宾根小组的丰富经验，将广泛研究用这种技术创建的新结构的结构和电子特性。

Perovskite photovoltaics have developed rapidly in recent years, reaching photovoltaic efficiencies well above 20% - close to the thermodynamic (Shockley-Queisser) limit. Furthermore, hybrid perovskites can be directly grown in 2D layered configuration by clever choice of the organic cation, thus creating a prestructured layer stack. For these types of perovskites, stability is increased immensely, even if only a thin layer of 2D perovskite is used as a barrier on top of a thicker “3D” thin-film. In this project, we plan to address the astonishing physical properties of these materials and the influence of dimensionality using vacuum evaporation. Though 2D-perovskites have been demonstrated from solution in a self-layering manner, 2D-layering using highly precise vacuum evaporation techniques has not been shown. Within PHIVE-X, we will use the variability in crystal structure and electric properties of the perovskites to follow two main paths: Realization of vacuum-deposited, self-structured 2D perovskites and manufacturing of highly-precise thin-film stacks of alternating perovskites with different stoichiometry – forced 2D perovskites. The latter is exclusively viable using the unique film control of vacuum deposition. We thus widen the possible material choices and open up a completely new field of perovskite research. By precisely controlling stoichiometry during growth, variations in the materials alter the band gap and refractive index in the ultra-thin films. In particular, we intend to exploit the opportunities of this method in a comprehensive manner, like tuning the band gap by almost 0.8 eV via interchanging iodide and bromine, as well as methyl ammonium and formamidinium. Both paths will be applied to device concepts: Self-structured and forced 2D perovskites will be implemented in solar cells as well as light-emitting devices and investigated towards their performance and stability. With forced 2D perovskites, we will also effectively form double heterostructures and superlattices. If correctly tuned, carrier and light confinement create a range of opportunities for optoelectronic applications like perovskite lasers. The novel structures created with this technique will be extensively studied with regard to the structural and electronic properties, combining the extensive experience of the Dresden and Tübingen groups.