Illuminating building block evolution of metal-halide perovskite semiconductors from solutions to thin films (GLIMPSE)

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The goal of the GLIMPSE project is gaining fundamental insight into how metal-halide solution complexes determine the opto-electronic properties of 3D solid state metal-halide perovskite semiconductors. We will tackle these research questions in an interdisciplinary framework at the boundary between chemistry and physics utilizing strongly intertwined experimental and theoretical methods. The project is divided into the three aspects to identify structure, spectra and evolution of molecular metal-halide complexes during thin film formation. Experimentally, the coordination chemistry, geometry and structure of halido-plumbate complexes will be investigated with a combination of state-of-the-art X-ray spectroscopy techniques (EXAFS, XANES) as well as X-ray diffraction (XRD) and compared to theoretical density-functional theory (DFT) calculations. The binding strength of halide and solvents to the metal determined from DFT will be compared to chemical equilibrium constants determined from Benesi-Hildebrand analysis of absorption data. We will identify and rationalize the spectral fingerprints of metal-halide-solvent complexes in solution by means of optical spectroscopy complemented by first-principles calculations based on many-body perturbation theory (MBPT). The evolution of solution complexes representing 0D building blocks of 3D metal-halide perovskite semiconductors via low-dimensional 1D and 2D crystalline intermediates will be investigated by a combination of in-situ optical monitoring and correlative X-ray based techniques. These studies will be complemented by DFT and MBPT calculations on the crystalline intermediates, giving access to electronic, optical, and core-level excitations with state-of-the-art accuracy. The outcomes of this project will provide unprecedented insight into how the structure of metal-halide solution complexes (building blocks) determine morphology and opto-electronic quality, charge carrier dynamics, defects, defect tolerance and intrinsic degradation mechanisms of metal-halide perovskite thin films.