Superspace Architecture-Driven Energy Funneling in Layered Halide Perovskite Nanoplatelets.

Hazra, Vishwadeepa; Aggarwal, Naresh; Mal, Santanu; Ubaid, Mohammad; Pal, Koushik; Adarsh, K V; Bhattacharyya, Sayan · Adv Mater · 2026

basic_science · Level V

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Abstract

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<sub>2</sub>FA<sub>n</sub> <sub>-1</sub>[Sn<sub>0.022</sub>Pb<sub>0.978</sub>]<sub>n</sub>I<sub>3</sub> <sub>n</sub> <sub>+1</sub> (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.