Taming Phase Transitions in Two-Dimensional Hybrid Perovskites

Metal halide perovskites often exhibit phase transitions that occur near room temperature. Typically, efforts have focused on suppressing phase transitions for optimal device stability. Yet, strategies to control these phase transitions could lead to new applications in memory storage, thermal energy storage, and switchable optoelectronic devices. We demonstrate that we can control the temperature of the order-to-disorder phase transition of two-dimensional Ruddlesden Popper perovskites through alkyl cation alloying. We also connect structural transformations to changes in photophysical properties and show that changes in photoluminescence wavelength and intensity are tied to octahedral distortions in the perovskite crystal lattice. Last, using photoluminescence imaging, we image the dynamics of the phase transition and show that the nature of these dynamics depends on the alkyl cation length.