Pressure-Driven Circularly Polarized Luminescence Enhancement and Chirality Amplification

Area of Science:

• Materials Science
• Solid-State Chemistry
• Optoelectronics

Background:

• Achieving high-purity circularly polarized luminescence (CPL) in low-dimensional chiral perovskites is hindered by strong electron-phonon coupling due to octahedral distortions.
• Investigating piezoluminescence in chiral perovskites offers a pathway to tune CPL properties under mechanical stress.

Purpose of the Study:

• To systematically investigate the circularly polarized piezoluminescence behaviors of novel chiral perovskites.
• To explore the potential of pressure-induced color changes and chirality amplification in these materials.

Main Methods:

• Synthesis and characterization of six novel chiral perovskites: (S/R-3-XPEA)2PbBr4 (X = F, Cl, Br).
• Systematic investigation of piezoluminescence under varying compressive pressures.
• High-pressure structural characterization and theoretical calculations.

Main Results:

• (S/R-3-ClPEA)2PbBr4 shows significant piezofluorochromism, shifting from yellow to ultrahigh-purity deep-blue CPL with increasing pressure.
• Under 2.5 GPa, deep-blue CPL intensity in (S/R-3-ClPEA)2PbBr4 increases tenfold, and luminescence asymmetry factors (g_lum) amplify from ±0.03 to ±0.1.
• (S/R-3-BrPEA)2PbBr4 exhibits a similar response, achieving deep-blue CPL at 1.7 GPa, while (S/R-3-FPEA)2PbBr4 maintains yellow CPL.

Conclusions:

• Pressure-enhanced halogen bonds reduce organic cation penetration into perovskite frameworks, suppressing electron-phonon coupling.
• This suppression is crucial for achieving ultrahigh-purity deep-blue CPL and chirality amplification in (S/R-3-BrPEA)2PbBr4 and (S/R-3-ClPEA)2PbBr4.
• The findings pave the way for developing advanced CPL materials responsive to mechanical stimuli.