For DPA-based quasi-2D HPs (Figure and Figure ), n=1-5 2D phases (components 2-4 in Figure ) concurrently emerge with a similar trend across the entire compositional range, particularly prominent at low 3D concentrations (<30%). The stable 3D-like HPs emerge at a large compositional range of 20-85%. These observations imply that the formation of low-n 2D phases is much more restricted than those in ThEA and PEA-based counterparts. Note that the PL peak of the 3D-like HPs exhibits an almost identical PL center to that of α-CsPbI3 HP (Component 2), suggesting that the 3D-like phase in DPA-based quasi-2D HP has thick inorganic lattices in the HP lattices (i.e., very high n values) on par with those in bulk 3D CsPbI3 HPs . Presumably, the incomplete surface coverage of DPA, as a result of steric hindrance , provides appropriate strain to the inorganic lattice to manifest the cubic α-CsPbI3 HP phase, which cannot be achieved by using the conventional spacer cations.