Chiral-deformation-induced polarons as a design principle for white-light emission in 2D organic halide perovskites

Two-dimensional (2D) chiral halide perovskites have emerged as promising platforms for light emission, yet the microscopic origin of their broadband photoluminescence remains unresolved. Here, we reveal a mechanism whereby molecular chirality induces structural asymmetry in the inorganic lattice, giving rise to chiral polar deformations that stabilize large polarons, providing a direct pathway toward white-light emission. By integrating tight-binding effective models, first-principles simulations, and structural-optical characterization of two 2D chiral lead bromide perovskites based on the S-enantiomer of the chiral \ensuremath{\alpha}-methylbenzylamine (MBA) and 1-cyclohexylethylamine (CHEA) organic spacers in the form of ${(\text{S-MBA})}_{2}{\mathrm{PbBr}}_{4}$ and ${(\text{S-CHEA})}_{2}{\mathrm{PbBr}}_{4}$, we formulate a predictive framework that links symmetry breaking to electronic localization. The combined results reveal how molecular packing governs the emergence of polarons and tunes the spectral width of emission. The more distorted CHEA-based compound supports a continuum of midgap states and exhibits broadband white-light emission, while its MBA analog remains narrowband. Effective models show that long-range asymmetric potentials hybridize with extended states to produce spectrally broad recombination. This work establishes a design principle in which chirality distortions induced in the inorganic layers enable polaron formation and lattice polarization, offering a route toward single-component white-light emitters with intrinsic asymmetry and tunable spectra.