Superspace Architecture‐Driven Energy Funneling in Layered Halide Perovskite Nanoplatelets

Layered hybrid perovskites offer a versatile platform for tailoring light‐matter interactions, where alternative stacking of inorganic and organic layers creates complex couplings that disrupt the conventional crystal symmetry. Standard crystallographic models fall short of capturing the temperature‐dependent stacking disorder and multiplet excitonic features in these systems. Here, we introduce a four‐dimensional superspace framework, employing a phenomenological atomic modulation function, to describe the symmetry‐breaking interactions in Ruddlesden–Popper L 2 FA n ‐1 [Sn 0.022 Pb 0.978 ] n I 3 n +1 (L: oleylamine, n ≥ 2) nanoplatelet superlattices. Temperature‐tunable optical spectra reveal microcavity‐like excitonic confinement, while ultrafast transient absorption spectroscopy uncovers sub‐picosecond energy funneling through modulated quantum wells, facilitating a measurable and stable self‐powered photoresponse across a broad spectral range at room temperature. A rare coexistence of negative thermal expansion and quenching arises from anisotropic octahedral distortions and electron–phonon interactions. These findings establish a new structure‐function paradigm for designing thermally reconfigurable optoelectronic materials via engineered lattice modulation in hybrid perovskite superstructures.