title: Chemical and electronic structure of Cu2O, NiO, and Cu2O-NiO combinatorial material libraries as hole-transport material for halide perovskite solar cells
Creators: name: Bodenstein-Dresler, Lucas
Publisher: name: Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU)
Year: 2024
Subjects: subject: Dissertation, interface, spectroscopy, XPS, UPS, IPES, perovskite, HTL, combinatorial material libraries, data analysis, paython

description: Admist the rising global temperatures and the rapid change of the overall climate, renewable energy technologies are of rising importance. Solar energy is one of the possible energy sources to harvest and significant progress has been made in this research field in recent decades. New types of materials, such as metal halide perovskite (MHP), are a rising stars in the field of solar cell (SC)-technologies. However, for each new material, its composition and properties must be measured, analyzed and understood, to guarantee a growth in efficiency and stability. One of these analysis methods is X-ray photoelectron spectroscopy (XPS), which allows the revelation of the surface composition of materials as well as their electronic and chemical properties. Unfortunately, XPS is known to be a relatively slow method, which limits its applicability its use for large data sets, such as combinatorial libraries. This work aims to establish XPS as a high-throughput analysis method. This is done by introducing an integration-analysis method, which can give a good estimation of the elemental composition on-the-fly during a measurement, even without the need of a large signal-to-noise ratio. This is done on a (72 × 72)mm2 CuxNi1−xOy (CuNiO) compositional library, which is used to show how characterization and evaluation routines can be optimized to improve the throughput in XPS, especially for combinatorial studies. Furthermore, a new analysis script is introduced, which helps to analyze large XPS data sets, while using an active-Shirley background (SBG) and linking the different material properties with each other. Another focus of this thesis is the investigation of interfaces between the combinatorial CuNiO library and two types of MHP materials: MA0.16FA0.79Cs0.05Pb(I0.84Br0.16)3 (MAFACsPbIBr) and FA0.85Cs0.15PbI3 (FACsPbI). With the goal to find possible a relationships between the interface structure and stability of the perovskite. To this end, first bare binary metal oxide (MO) (Cu2O and NiO) are measured to gain basic knowledge for the scaled-up analysis of the interface properties of the libraries. This also includes the change of i.e. oxidation states and other properties of plasma-cleaned samples, which is a necessary step in the SC stack production. As a next step, different two libraries have been investigated. There, we show the effect of different plasma cleaning strengths on the elemental composition of these libraries and how the elemental gradient influences it. Finally, the knowledge gained is used when analyzing the effect of the underlying hole transport layer (HTL) properties on the halide perovskites, by using a thickness gradient orthogonal to the Cu-Ni-gradient. Here, we show that the in-vacuum measured MAFACsPbIBr has the largest loss of organic component on the Cu-rich side, which is not the case for the FACsPbI. For this type of perovskite, the plasma cleaning-method (Cu(I)-amount) is of greater importance, where we can show that the reduction of the Cu(I) is more important to generate a (in vacuum) stable perovskite. Additionally, we show the strong influence of the combination of X-rays and vacuum on perovskite degradation.