The observed correlations between the phase emergence behaviors and the selection of spacers collectively infer distinctive principles for designing quasi-2D HP matrices. In general, heavy molecular spacers manifest the growth of high-n or 3Dlike HP phases, which are also more stable than the pure 3D CsPbI3 counterpart and therefore benefit PV applications. However, at the same time, this simultaneously causes the strong emergence of low-n (particularly, n=1) 2D HPs at the bottom, which act as an energetic barrier for charge transport. The DJ-type spacer can greatly mitigate such vertical phase inhomogeneity, although this adversely compromises the phase stability. While the spacers having aromatic rings offer better stability to the 3Dlike phases compared to the aliphatic chain, practically, the phenyl ring is more advantageous to phase stability than other heterocyclic rings.