Constructing a photoferroelectric semiconductor by regulating non-covalent interactions through halogen substitution.

Area of Science:

• Materials Science
• Solid-State Chemistry
• Crystallography

Background:

• Molecular ferroelectrics offer designability and multifunctionality, with non-covalent interactions crucial for their construction.
• Challenges exist in balancing non-covalent interaction strength and reversibility, and achieving long-range order in molecular ferroelectrics.
• Systematic studies of non-covalent interactions are key to developing high-performance molecular ferroelectrics.

Purpose of the Study:

• To investigate the role of non-covalent interactions in constructing high-performance molecular ferroelectrics.
• To induce ferroelectricity by regulating non-covalent interactions using halogenated amines.
• To explore the effect of halogen substitution on the properties of hybrid perovskite ferroelectrics.

Main Methods:

• Introduction of halogenated amines with large dipole moments into inorganic layers.
• Halogen substitution strategy: introducing chlorine (Cl) atoms onto PA+ (n-propylaminium) cations.
• Synthesis and characterization of the hybrid perovskite photoferroelectric semiconductor (Cl-PA)2PbBr4.

Main Results:

• A novel hybrid perovskite photoferroelectric semiconductor, (Cl-PA)2PbBr4, was successfully synthesized.
• The material exhibits a large piezoelectric response (d33 = 36 pC/N) and a high Curie temperature (Tc = 365 K).
• Chlorine substitution increased the dipole moment (from 1.2 D to 3.3 D) and promoted directional ordering of cations, inducing ferroelectricity.

Conclusions:

• Non-covalent interactions, specifically hydrogen bonding and halogen-halogen interactions, are critical for the directional ordering of organic cations and the generation of ferroelectricity.
• Halogen substitution significantly enhances the dipole moment and dynamic freedom of organic cations, promoting ferroelectric phase transitions.
• This work highlights the importance of molecular-level design and non-covalent interactions in developing advanced ferroelectric materials.