To systematically explore the spacer-dependent phase emergence behaviors in the corresponding quasi-2D HPs, we utilize a high-throughput automated experimental workflow . Our designed workflow allows maximal acceleration of the synthesischaracterization-analysis cycle with much cheaper costs, enabled by the incorporation of rapid characterization methods and easy to interpret ML methods in the discovery loop. Here, the precursor solutions with different 2D:3D composition ratios -prepared via combinatorial mixing of 3D CsPbI3 and respective 2D HP precursors, as shown in Figure -are drop-casted onto the glass substrates. Subsequent thermal annealing at 95 o C allows for the synthesis of quasi-2D HP film arrays with the respective spacer cations. The resulting film arrays are quickly transferred to an optical reader to collect photoluminescence spectra from both the top and bottom surfaces over time. This allows us to identify the distinct phase emergence behaviors and vertical phase inhomogeneities, and assess their stabilities in each quasi-2D HP combinatorial library (Figure ). Here, we select five representative spacer cations as precursors: BA, BDA, ThEA, PEA, and DPA. In contrast to BA with a short alkyl chain, PEA, ThEA and DPA have one or two aromatic rings in the corresponding molecular structures, allowing for understanding the role of aromatic rings in phase emergence behaviors and stabilities; ThEA and DPA respectively provide additional insights into the chemical impact of heterocycle and the number of the aromatic ring on the phase growth of quasi-2D HPs. Also, BDA represents the phase growth features of DJ-type perovskite. Figure -g exhibit the initial top-emitting PL spectra of the quasi-2D HP films as a function of 3D CsPbI3 composition ratios with different 2D HP endmembers, clearly visualizing the differences in phase emergence behaviors along the combinatorial libraries (the photographs of the corresponding film arrays and the entire datasets of time-evolved PL spectra for each combinatorial library are shown in Figure and Figure -S7, respectively). In contrast to 100% 3D CsPbI3 film, where the nonperovskite yellow phase dominantly emerges, the incorporation of 2D HP endmember manifests the growths of 2D or 3D-like HP phases involving the corresponding PL spectra. For all cases, in addition to the n=1 2D phase that exclusively formed at 0% -evidenced by the single PL peak centered at ~510-520 nm, PL spectra of the highern 2D phases emerge with increasing the 3D CsPbI3 composition ratios. However, the trends in phase emergence behaviors show distinctive features depending on the selection of spacer cation.