Integrating Robotic High-Throughput Processing with Synchrotron Based In Situ Multimodal Analysis—Homogenous Crystallization of Mixed Br-I Perovskites

Optoelectronic material properties and especially conversion efficiencies of next-generation semiconductors are a result of the complex interplay between precursors, intermediates, spectators and products during synthesis processes. Therefore, the discovery of optimized synthesis processes has become an important part in material discovery approaches. A knowledge based discovery and tuning of synthesis processes requires a fundamental understanding of its systematics, pathways and kinetics. Due to the complexity of synthesis interactions, a multitude of experiments with a wide variation of parameters, investigated from complemental perspectives, is required.<br/><br/>To this extend we developed a platform (<i>in-FORM</i>), which integrates robotic high-throughput solution processing with synchrotron based in-situ multimodal process analysis. It is based on a small-footprint, robotic, roll-to-roll slot-die coating system, which is fully integrated into a hard X-ray beamline for real-time in-situ process analysis at the MAX IV synchrotron. We measure simultaneously and at the same spot from the same incident X-ray beam a combination of X-ray spectroscopy (X-ray absorption and fluorescence), X-ray diffraction (XRD) and X-ray excited optical luminescence (XEOL). This allows for a complementary investigation of the local structure, crystalline phase, chemical composition, oxidation states, and optoelectronic properties, unraveling formation and evolution processes during and after slot-die ink deposition.<br/>Aiming to optimize the synthesis of mixed bromide-iodide metal-halide perovskites for a wide range of resulting absorber band-gaps while achieving high opto-electronic material quality, we utilized our in-situ platform. We investigated the full formation process, from precursor solutions to final films, under a wide range of synthesis parameters using a combinatorial approach. Our results show how the choice of solvents and co-solvents determines Br/I intermixing and segregation during the synthesis process. Measurements with high-temporal resolution (10ms) during rapid gas quenching reveal how rapid quenching processes can be utilized to achieve homogenous Br/I distributions. By enabling a fundamental understanding of the complex interplay between solvents and intermediates, we pave the way towards the development of greener solvent processes and environmental friendly up-scaling.