Impact of Organic Spacers and Dimensionality on Templating of Halide Perovskites

Two-dimensional (2D) halide perovskites (HPs) are promising materials for various optoelectronic applications; yet, a comprehensive understanding of their dynamics is still elusive. Here, we offer insight into the dynamics of prototypical 2D HPs based on MAPbI₃ as a function of linker molecule and the number of perovskite layers using atomic-scale simulations. We show that the layers closest to the linker undergo transitions that are distinct from those of the interior layers. These transitions can take place anywhere between a few tens of Kelvin degrees below and more than 100 K above the cubic–tetragonal transition of bulk MAPbI₃. In combination with the thickness of the perovskite layer, this enables one to template phase transitions and tune the dynamics over a wide temperature range. Our results thereby reveal the details of an important and generalizable design mechanism for tuning the properties of these materials.