Transferring the high power conversion efficiencies (PCEs) of spin-coated perovskite solar cells (PSCs) on the laboratory scale to large-area photovoltaic modules requires a significant advance in scalable fabrication methods. Digital inkjet printing promises scalable, material, and cost-efficient deposition of perovskite thin films on a wide range of substrates and in arbitrary shapes. In this work, high-quality inkjet-printed triple-cation (methylammonium, formamidinium, and cesium) perovskite layers with exceptional thicknesses of >1 µm are demonstrated, enabling unprecedentedly high PCEs > 21% and stabilized power output efficiencies > 18% for inkjet-printed PSCs. In-depth characterization shows that the thick inkjet-printed perovskite thin films deposited using the process developed herein exhibit a columnar crystal structure, free of horizontal grain boundaries, which extend over the entire thickness. A thin film thickness of around 1.5 µm is determined as optimal for PSC for this process. Up to this layer thickness X-ray photoemission spectroscopy analysis confirms the expected stoichiometric perovskite composition at the surface and shows strong deviations and inhomogeneities for thicker thin films. The micrometer-thick perovskite thin films exhibit remarkably long charge carrier lifetimes, highlighting their excellent optoelectronic characteristics. They are particularly promising for next-generation inkjet-printed perovskite solar cells, photodetectors, and X-ray detectors.