Temporal stability of the quasi-2D HP phases in ThEA-and PEA-based systems, after exposing the films for 10 hours in ambient atmosphere, are also assessed (Figure and). Appreciable intermediate-n 2D HPs emerge in the ThEA-based quasi-2D HP composition space, at the expense of the 3D-like phase. In contrast, marginal changes in phase emergence behaviors are observed across the compositional space of the PEA-based system. These observations imply that PEA cation offers better phase stability compared to ThEA. It is known that PEA in quasi-2D HPs enhances phase stability, as the phenyl ring can protect the inorganic lattice against external stimuli such as O2 and H2O . Considering this, the poor stability of ThEA-based quasi-2D HP is likely associated with the heterocyclic structure of thiophene; this can offer a different scenario in chemical interactions which cannot benefit the stability of the HP lattice.