Pressure-Driven Structural and Optoelectronic Tuning of Cl-Substituted 2D Lead Halide Perovskite (ClPMA)₂PbI₄

Area of Science:

• Materials Science
• Solid State Physics
• Chemistry

Background:

• Two-dimensional hybrid perovskites are promising optoelectronic materials.
• Understanding their behavior under pressure is crucial for device applications.
• Chlorine functionalization offers a route to tune material properties.

Purpose of the Study:

• To systematically investigate the high-pressure structural, mechanical, and optoelectronic properties of chlorine-functionalized 2D hybrid perovskite (ClPMA)2PbI4.
• To elucidate the relationship between structural changes and optoelectronic response under hydrostatic compression.
• To assess the potential of (ClPMA)2PbI4 for strain-engineered optoelectronic devices.

Main Methods:

• In situ high-pressure synchrotron powder X-ray diffraction (HP-PXRD) up to 6.18 GPa.
• High-pressure photoluminescence spectroscopy (HP-PL) to monitor optical properties.
• First-principles density functional theory (DFT) calculations for structural and electronic analysis.

Main Results:

• Anisotropic lattice contraction observed, with significant changes along the c-axis.
• Bulk modulus determined as 16.8 GPa, with amorphization onset near 6.18 GPa.
• Progressive PbI6 octahedral flattening and enhanced intermolecular interactions under pressure.
• Red shift in photoluminescence from 525.2 nm to ~630.5 nm, indicating bandgap narrowing.
• DFT confirmed pressure-dependent direct-gap evolution and maintained band alignment.

Conclusions:

• (ClPMA)2PbI4 exhibits significant structural and optoelectronic tunability under high pressure.
• The material displays complex elastic behavior with coexisting auxetic and elastic deformation pathways.
• Pressure-induced amorphization and bandgap narrowing impact photoluminescence intensity and spectral position.
• Findings highlight the potential of (ClPMA)2PbI4 for advanced strain-engineered optoelectronic applications.