Advisor: Prof. Juan-Pablo Correa-Baena

will defend a doctoral thesis entitled,

The Role of Lattice Distortions in the Excitonic Fine Structure and Strong Light-Matter Coupling of Two-Dimensional Perovskites

On

Monday, April 13th  at 10 a.m.

Pettit Microelectronics Room 102A

And virtually via Zoom

https://gatech.zoom.us/j/92878908653?pwd=Rc8Mo0DtomJ2O1bYrKaABivRrm6hBh.1

Committee

            Prof. Juan-Pablo Correa-Baena – School of MSE, Georgia Institute of Technology (advisor)

            Prof. Natalie Stingelin – Schools of MSE & ChBE, Georgia Institute of Technology

      Prof. Emma Hu – School of MSE, Georgia Institute of Technology

            Prof. Vinod Menon – School of Physics, City University of New York

            Prof. Carlos Silva-Acuña – School of Physics, Université de Montréal

      Prof. Ajay Ram Srimath Kandada – School of Physics, Wake Forest University

Abstract

Two-dimensional (2D) hybrid organic-inorganic halide perovskites are semiconductors that host strongly confined excitons and exhibit optical properties well suited for studying light-matter interactions. Their large exciton binding energies, strong oscillator strengths, tunable optical response, and relatively low non-radiative recombination rates make them promising candidates for light-emitting devices such as lasers and LEDs. At the same time, they possess a soft, deformable lattice whose behavior depends strongly on chemical composition and crystallographic structure. However, the connection between structural distortions, chemical composition, and excited-state behavior in these materials remains incompletely understood. This thesis studies how changes in crystal structure, spacer-cation chemistry, and lattice dynamics can be used to tailor the optical properties of two-dimensional halide perovskites.

Chapters 1 and 2 introduce lower-dimensional perovskites and strong light-matter coupling. Chapter 3 shows that the fine structure of the exciton reservoir can limit radiative pumping efficiency in PEA2PbI4 microcavities. Chapter 4 demonstrates that a spacer-cation substitution can modify the structural dynamics of the inorganic framework, inducing changes in exciton-phonon coupling and polaritonic response. Finally, chapter 5 explores the ultrafast structural response of two-dimensional perovskites after photoexcitation using time-resolved wide-angle X-ray scattering, revealing a transient out-of-plane lattice modulation. This thesis highlights the role of the crystallographic structure in determining the optical response of 2D perovskites.