Triiodide perovskites CsPbI3, CsSnI3, and FAPbI3 (where FA is formamidinium) are highly promising materials for a range of optoelectronic applications in energy conversion. However, they are thermodynamically unstable at room temperature, preferring to form low-temperature (low-T) non-perovskite phases with one-dimensional anisotropic crystal structures. While such thermodynamic behavior represents a major obstacle toward realizing high-performance devices based on their high-temperature (high-T) perovskite phases, the underlying phase transition dynamics are still not well understood. Here we use in situ optical micro-spectroscopy to quantitatively study the transition from the low-T to high-T phases in individual CsSnI3 and FAPbI3 nanowires. We reveal a large blueshift in the photoluminescence (PL) peak (~38 meV) at the low-T/high-T two-phase interface of partially transitioned FAPbI3 wire, which may result from the lattice distortion at the phase boundary. Compared to the experimentally derived activation energy of CsSnI3 (~1.93 eV), the activation energy of FAPbI3 is relatively small (~0.84 eV), indicating a lower kinetic energy barrier when transitioning from a face-sharing octahedral configuration to a corner-sharing one. Further, the phase propagation rate in CsSnI3 is observed to be relatively high, which may be attributed to a high concentration of Sn vacancies. Our results could not only facilitate a deeper understanding of phase transition dynamics in halide perovskites with anisotropic crystal structures, but also enable controllable manipulation of optoelectronic properties via local phase engineering.

钙钛矿三碘化物CsPbI 3，CsSnI 3和FAPbI 3（其中FA为甲ami ）是在能量转换中的一系列光电应用中极有希望的材料。但是，它们在室温下是热力学不稳定的，它们倾向于形成具有一维各向异性晶体结构的低温（低T）非钙钛矿相。尽管这样的热力学行为是实现基于高温（高T）钙钛矿相的高性能器件的主要障碍，但仍不能很好地理解其潜在的相变动力学。在这里，我们使用原位光学显微技术定量研究各个CsSnI从低T相到高T相的转变3和FAPbI 3纳米线。我们揭示了部分过渡的FAPbI 3线的低T /高T两相界面处的光致发光（PL）峰（〜38 meV）中存在较大的蓝移，这可能是由于相界处的晶格畸变引起的。与实验得出的CsSnI 3的活化能（〜1.93 eV）相比，FAPbI 3的活化能相对较小（〜0.84 eV），这表明从面部共享的八面体构型过渡到转角时，动能垒较低。分享一个。此外，CsSnI 3中的相位传播速率观察到较高的Sn空位率。我们的结果不仅可以促进对具有各向异性晶体结构的卤化钙钛矿中相变动力学的更深入了解，而且还可以通过局部相工程实现对光电特性的可控操纵。