Work

Structural dynamics of low-dimensional lead-free azetidinium metal halides: a Raman spectroscopic study

Year: 2026

Type: article

Abstract: Lead-free hybrid metal halides have been attracting attention for their potential in various optoelectronic applications due to their appropriate bandgap, ease of fabrication, and bandgap tunability. Recently, several low-dimensional lead-free azetidinium metal halides have been successfully synthesized. The fundamental nature of the phase transitions in these materials arises from the intermolecular dynamics of the inorganic octahedral framework and the orientation of the A-site cations. In this study, we performed temperature-dependent Raman spectroscopy on eight different lead-free azetidinium metal halides to investigate the correlation between vibrational energy shifts and structural phase transitions. We utilized 785 nm laser excitation to characterize the [BX 6 ] octahedral modes and observed distinct anomalies at the phase transition temperatures in select compounds. The 532 nm laser excitation wavelength was used to detect azetidinium vibrational modes. Although direct tracking of ring puckering and deformation modes was limited by weak signals, analysis of the temperature dependence of the CH 2 mode revealed a second-order transition driven by the azetidinium cations. Moreover, the observed intensity variations provided strong evidence for an order-disorder transition associated with the azetidinium dynamics. These results underscore the critical role of azetidinium molecular behavior in mediating phase transitions in hybrid halide systems.

Source: Physica Scripta

DOI: 10.1088/1402-4896/ae87df