For all cases, the -NH3 + peak undergoes notable downfield shifts (~0.02 ppm) when the inorganic precursors are incorporated, indicating the strong chemical interaction between the ammonium group and the inorganic precursors (Figure ). In addition, for BA, the characteristic peaks of hydrogens at α-carbons also exhibit appreciable downfield shifts in the precursor solution (Figure and Figure ), indicating that partial electron transfer from BA to the inorganic precursors occurs. Note that the progressive weakening of the 1 H downfield shifts is observed from β-to δ-protons position where the latter does not exhibit appreciable peak shift. This suggests that the electrostatic interaction mainly takes place in the ammonium group. In BDA, the protons at both the α-and β-carbon exhibit strong and comparable downfield shifts (~0.016 ppm) when the inorganic precursors are present (Figure and Figure ). This indicates the existence of a strong chemical interaction between the inorganic ions and the BDA molecules -across the entire molecular structure. Presumably, two interactive sites (i.e., ammonium groups) in BDA manifest tight coordination with the HP building blocks in the solution phase (Figure ). Such strong chemical interaction between spacer and inorganic building blocks not only offers slow crystallization kinetics but also maintaining the ionic coordination during the entire film fabrication process -starting from liquid-air (top) to the liquid-substrate (bottom) interfaces. This likely mitigates the vertical phase inhomogeneity of the quasi-2D HP matrix. However, as the spacer-precursor interaction is too strong, some of the 3D CsPbI3 precursors cannot be involved for the crystallization of quasi-2D HP lattice. Subsequently, a separate crystallization of these 3D precursors take place, which are likely form δ-CsPbI3 that are intercalated into the film matrix, due to the thermodynamic incompatibility of the α-HP phase at such a low annealing temperature.