Fluorescence Emission Is Highly Structure-Dependent in Hybrid Lead Halides

Area of Science:

• Materials Science
• Solid-State Chemistry
• Photophysics

Background:

• Hybrid lead halide perovskites are promising for fluorescent displays and LEDs.
• Understanding the photoluminescence mechanism in 2D perovskites with varied inorganic skeletons is limited.
• Existing luminescent materials often rely on functional molecular and rare-earth metal ions.

Purpose of the Study:

• To investigate the influence of different layered inorganic frameworks on the photoluminescence properties of hybrid lead halide perovskites.
• To synthesize and characterize three novel organic-inorganic hybrid materials with distinct inorganic structures.
• To elucidate the photoluminescence mechanism through theoretical and experimental analyses.

Main Methods:

• Synthesis of three hybrid materials: (MACH)₂·PbBr₄ (Prv-1), (2-MPQ)·PbBr₄ (Prv-2), and (TMBA)₄·Pb₃Br₁₀ (Prv-3).
• Structural characterization and orientation determination ((100) for Prv-1, (110) for Prv-2, [Pb₃Br₁₀] for Prv-3).
• Photoluminescence measurements and theoretical computational studies, including frontier molecular orbital (FMO) analysis.

Main Results:

• Prv-1 exhibits strong blue-violet fluorescence, Prv-2 shows weak luminescence, and Prv-3 emits bright orange light.
• Electronic structures are highly dependent on distorted [PbBr₆] octahedra.
• All materials are direct band gap semiconductors (2.79, 2.97, 2.76 eV) with distinct conduction bands; Prv-3's HOMO/LUMO are derived from inorganic/organic parts.

Conclusions:

• The photoluminescence mechanism is explained by electronic energy levels influenced by the inorganic skeleton.
• Structural variations in hybrid lead halide perovskites significantly alter their luminescent color and intensity.
• This research provides strategies for designing novel perovskite materials with tailored structure-property relationships.