Chemical Vapor Deposited 3D and 2D Hybrid Halide Perovskite Films: Insights into Phase Stability and Exciton Dynamics*

Chemical vapor deposition (CVD), a low-cost and scalable deposition technique, allows the growth of halide perovskite thin films without the use of solvents. Using either a two or a three-step CVD process, we show the versatility of this process in the growth of phase stable 3D and 2D lead-halide perovskite films. We discuss temperature dependent X-ray diffraction and photoluminescence measurements from CVD grown 3D and 2D hybrid halide perovskite films, shedding light on phase stability, exciton binding energies, and exciton-phonon interactions in these systems. The luminescence properties of the prototypical 2D lead-iodide perovskite films with butylammonium (BA) versus phenylethylammonium (PEA) show large differences with the latter showing a single photoluminescence peak, highlighting the lack of defect states.  Detailed results of excitonic dynamics using ultrafast transient absorption  from 2D hybrid halide perovskites with BA and PEA will be discussed. Our results reveal the important potential utility of a relatively simple CVD growth method for hybrid halide perovskite films, which affords a significantly higher degree of controllability of the growth of these materials than that of other methods.