ThEA-and PEA-based quasi-2D HPs exhibit softer surface morphologies than BA and BDA counterparts. ThEA-based film exhibits angulated surface textures, likely attributed to the formation of small-n 2D HP phases. Also, rectangular particles exhibiting 445 nm CL are intercalated to the film surface (Figure and), indicating that δ-CsPbI3 also emerges in this system. Note that the area exhibiting the local δ-CsPbI3 signals is smaller than that in the BA-based system. These suggest that ThEA offers better stability of the 3D-like phases than BA, though it is still insufficient to realize PV-grade films. The PEA-based film renders a flat and smooth surface morphology, though some of the areas exhibit collapsed features. Note that the local spots emitting δ-CsPbI3 are notably reduced and there was no appreciable structural feature correlating with the emission spots (Figure ). This indicates that PEA offers much more improved phase stability of quasi-2D HPs than ThEA, thereby suppressing phase deformation. Meanwhile, stronger CL intensities of 3D-like HPs are observed along the cracked boundaries in the films. Such a distinct local contrast in 3D-like HP CL indicates that substantial chemical inhomogeneities are manifested in the film surface, which can disturb the energetic landscape and thereby hamper efficient charge transport.