Boosting Self-Trapped Exciton Emission via Interlayer Pillaring in Layered Lead Halide Frameworks

Corrugated layered hybrid lead halides have emerged as a promising class of intrinsic broadband self-trapped exciton (STE) emitters for single-component white-light emission. However, regulating the structure to improve photoluminescence performance while maintaining a high intrinsic stability remains challenging. In this study, we introduce an elongated and nonconjugated biscyclohexyl dicarboxylate ligand to pillar two new members of ultrastable layered lead halide frameworks. Both compounds exhibit broad-band emission with large Stokes shifts, characteristic of STE-mediated radiative recombination. Rational modulation of the organic pillar lengths effectively increases the dielectric mismatch between the inorganic layers and the organic spacers, boosting the photoluminescence quantum yields from 17.2% in a cyclohexyl-based framework to 33.4% in its biscyclohexyl analogue. In addition, the biscyclohexyl-based bromide framework exhibits enhanced STE emission compared with its chloride counterpart, attributed to a greater degree of out-of-plane distortion and structural corrugation that favors populated STE states. Moreover, these layered frameworks maintain high crystallinity and stable emission after treatment under aqueous conditions across wide pH ranges, demonstrating excellent structural robustness. Mechanistic studies indicate that the broadband emission originates from strong electron-phonon coupling and enhanced exciton confinement induced by the dielectric spacer. This work provides a novel strategy for designing high-efficiency, single-component, broadband luminescent materials.