Structural variations in (001)-oriented layered lead halide perovskites, templated by 1,2,4-triazolium.

Area of Science:

• Materials Science
• Solid-State Chemistry
• Crystallography

Background:

• Hybrid organic-inorganic perovskites are promising materials for various applications.
• Layered perovskites, particularly Ruddlesden-Popper (RP) phases, exhibit unique structural and electronic properties.
• Understanding structure-property relationships is crucial for designing new functional materials.

Purpose of the Study:

• To synthesize and characterize a new hybrid lead(II) halide perovskite, (TzH)2PbCl4.
• To investigate the structural phase transition of (TzH)2PbCl4 using variable temperature single crystal X-ray diffraction.
• To report a second polymorph of the bromide analogue, (TzH)2PbBr4-II, and discuss structural relationships.

Main Methods:

• Single crystal X-ray diffraction at variable temperatures.
• UV-Vis spectroscopy.
• Crystallographic analysis.

Main Results:

• A new (001)-oriented layered perovskite, (TzH)2PbCl4, derived from the n=1 RP type was synthesized.
• A structural phase transition was observed between 125 K and 173 K, involving a change from Cmcm to a chiral P212121 space group with tripled unit cell volume.
• The band gap of (TzH)2PbCl4 was determined to be 3.30 eV via UV-Vis spectroscopy.
• A second polymorph of (TzH)2PbBr4-II was identified.

Conclusions:

• The hybrid perovskite (TzH)2PbCl4 displays a temperature-dependent structural phase transition.
• The study expands the known structural diversity of hybrid lead halide perovskites.
• The findings provide insights into the structural relationships among related perovskite variants.