Circular Dichroism in Achiral-Chiral Mixed Cation Two-Dimensional Hybrid Perovskites

Student’s name: Jack Hannon Home Institution: Lehigh University NNCI Site: RTNN at UNC Chapel Hill REU Principal Investigator: Dr. Wei You - Department of Chemistry, UNC Chapel Hill REU Mentor: Camryn Gloor - Department of Chemistry, UNC Chapel Hill Abstract: The utility of hybrid perovskites in optoelectronic devices is largely due to their extensive tunability. For instance, specific components of a perovskite can be tailored to introduce the chiroptical properties necessary for application in spintronics and circularly polarized light sources. Chiral organic spacer cations are often used to impart the desired chiroptical properties to hybrid perovskites, and recently, this premise has been extended to achiral-chiral mixed cation systems. Hybrid perovskites with a mixture of achiral and chiral organic spacer cations have produced circular dichroism (CD) signals with a different sign and magnitude than the related perovskite system containing only the chiral cation. This project aims to explore this phenomenon in more detail by analyzing mixed cation perovskite thin films of various chiral cations and achiral-chiral ratios. Absorbance, X-ray diffraction, and circular dichroism will be used to gain insight into the excitonic properties, novel mixed cation phases, and CD transformation for each cation pair and ratio. Uncovering the mechanisms that lead to changes in the CD signals of mixed cation systems will provide another method to tune the chiroptical properties of hybrid perovskites.