Reversible Medium-Dependent Solid–Solid Phase Transformations in Two-Dimensional Hybrid Perovskites

The thermodynamically favored phases
in a family of two-dimensional
(2D) hybrid perovskites, (C6H13NH3)2MCl4 (M = Cu2+, Mn2+, Cd2+), can be reversibly switched by changing the medium
in which particles are immersed. Differential scanning calorimetry
and X-ray diffraction show that the temperature of a known solid–solid
phase transition in the series of layered perovskites shifts to lower
temperature when exposing the particles to organic solvents. For the
Cu2+ and Cd2+ members of the series, the shift
in transition temperature changes the thermodynamically favored phase
at room temperature. Interactions between the solvent and the particle
surface alter the surface stress, thereby reducing the effective pressure,
leading to a change in transition temperature. The mechanism likely
explains some anomalous behavior in related 2D perovskites and could
factor into potential applications of hybrid perovskite-based materials.

二维（2D）杂化钙钛矿家族中，通式为(C₆H₁₃NH₃)₂MCl₄（M = Cu²+、Mn²+、Cd²+）的材料，其热力学稳定相可通过改变颗粒所处的浸没介质实现可逆切换。差示扫描量热法与X射线衍射结果显示，该系列层状钙钛矿中已被报道的固-固相变温度，在颗粒浸没于有机溶剂时会向低温方向偏移。对于该系列中Cu²+与Cd²+对应的成员材料，相变温度的偏移会改变室温下的热力学稳定相。溶剂与颗粒表面之间的相互作用会改变表面应力，进而降低有效压强，最终导致相变温度发生变化。该机制或可解释相关二维钙钛矿体系中的部分反常现象，同时可为杂化钙钛矿基材料的潜在应用提供理论支撑。