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

Area of Science:

• Materials Science
• Solid-State Chemistry
• Photophysics

Background:

• Layered hybrid lead halides are promising for broadband white-light emission via intrinsic self-trapped excitons (STE).
• Achieving high photoluminescence performance and stability in these materials is challenging due to structural regulation difficulties.

Purpose of the Study:

• To design and synthesize novel ultrastable layered lead halide frameworks with enhanced photoluminescence.
• To investigate the structure-property relationships governing STE emission and material stability.

Main Methods:

• Synthesis of new layered lead halide frameworks using elongated, nonconjugated biscyclohexyl dicarboxylate ligands.
• Characterization of structural, optical, and stability properties, including photoluminescence quantum yield (PLQY) measurements.
• Mechanistic studies involving electron-phonon coupling and exciton confinement analysis.

Main Results:

• Two new layered lead halide compounds with broad-band emission and large Stokes shifts were successfully synthesized.
• Increasing organic pillar length enhanced PLQY from 17.2% to 33.4% due to increased dielectric mismatch.
• The biscyclohexyl bromide framework showed improved STE emission over its chloride analogue, linked to greater structural distortion.

Conclusions:

• Rational ligand design offers a viable strategy for optimizing photoluminescence efficiency and stability in layered lead halides.
• The developed materials exhibit excellent structural robustness and tunable broadband emission, suitable for single-component white-light applications.
• Strong electron-phonon coupling and exciton confinement within the dielectric spacer are key to broadband STE emission.