Abstract: This thesis discusses studies performed by the author at the Fraunhofer Institute for Solar Energy Systems, ISE. The presented work focuses on the characterization of hybrid organic-inorganic halide perovskite materials used for photovoltaic application. In an in situ study of the perovskite crystal formation, multiple stages are identified. Taking advantage of a graphite-based cell structure where both contacts are in place before the perovskite crystal formation occurs within the mesoporous scaffold, the photovoltaic performance along with optoelectronic properties are monitored in real time during the crystallization. As perovskite solar cells are prone to spatial heterogeneity, spatially resolved characterization techniques mainly based on photoluminescence spectroscopy, light beam-induced current and thermography are employed to analyze non-uniform optoelectronic properties and quantify local loss mechanisms. A novel characterization method is introduced by the author, allowing for the quantitative assessment of local loss mechanisms. The technique is demonstrated on blade coated perovskite solar cells, which represent a scalable deposition route, and it highlights the detrimental impact of layer non-uniformity on the overall solar cell performance. It presents a powerful tool for the targeted improvement of layer homogeneity and consequential benefit the enhancement of the cell efficiency. In high bandgap perovskite films made from a mixed cation and halide alloy, the local optoelectronic properties are analyzed with micrometer resolution. Non-uniform emission properties are revealed and related to the layer morphology. A subcell-selective analysis of monolithic two-terminal silicon perovskite tandem solar cells is presented, accessing the individual subcells by multi-wavelength photoluminescence spectroscopy. The mapping approach additionally yields spatial distribution of the photoluminescence emission, allowing for the identification of process influences on the two subcells. The results from this thesis generated insights about the perovskite crystal formation and spatial heterogeneities on different length scales. Overall, the findings support the targeted optimization of hybrid organic-inorganic halide perovskite solar cells.