Symposium EL06: Novel Perovskite Semiconductors and Optoelectronics

Benjamin Gallant, University of Birmingham

In Situ Atomic-Level Tracking of Thermal Transformations in Multi-Dimensional Halide Perovskites

Written by Md Afzalur Rab

Benjamin Gallant investigated the thermal stability and ion dynamics of metal halide perovskites across different structural dimensions, including 0D, 2D, and mixed 2D-3D systems. These materials are widely used in applications such as light-emitting diodes, scintillators for x-ray imaging, and high-efficiency perovskite solar cells. Despite their popularity, how these materials behave under thermal stress during device fabrication is not well understood. To explore this, Gallant used a combination of in situ variable temperature solid-state NMR (VT-NMR) and x-ray diffraction (VT-XRD). These techniques allowed real-time monitoring of structural and chemical changes at temperatures up to 500°C. The study found that several low-dimensional perovskites degrade at relatively low temperatures, below 250°C. There were also clear differences in how various perovskite structures undergo halide and ion migration.

In his poster presentation, Gallant highlighted that this ion migration behavior is crucial for thin-film devices where 1D and 2D perovskites are often used to stabilize 3D structures. Through VT-NMR, isotopes like ¹³³Cs, ²⁰⁷Pb, and ⁸⁷Rb were shown to be effective in detecting changes in ion mobility. Notably, NMR linewidths decreased by three orders of magnitude at higher temperatures, indicating increased ion mobility. The study also uncovered trace secondary phases that standard techniques like conventional XRD could not detect. These findings suggest that perovskite composition plays a significant role in halide migration and overall thermal behavior. Although the study did not introduce a new material, it brought novel insights into existing systems. The research offers valuable guidelines for improving the thermal and operational stability of perovskite-based devices. It also highlights the power of temperature-dependent NMR as a sensitive characterization tool. Overall, the findings are expected to influence future perovskite research and device engineering.