Synthesis and Analysis of the Optical Anisotropy of Cesium Lead Halide Perovskite Nanocrystals and Their Heterostructures

Abstract

This dissertation focuses on the synthetic development and study of the anisotropic optical properties of cesium lead halide perovskite nanocrystals and their heterostructures with gold. Three primary research objectives have emerged from this concept. Firstly, a synthetic approach based on the oxidation state of gold ions is developed for the fabrication of hybrid AuCsPbX3 nanoparticles or lead-free Cs2AuI AuIIIX6 perovskite nanoparticles. CsPbBr3 exhibits high-efficiency photoluminescence when gold nanoparticles are deposited on its surface, contrary to other metal-semiconductor heterostructure systems where the deposition of metal nanoparticles quenches the photoluminescence. Additionally, preliminary measurements of optical anisotropy suggest that the deposition of gold nanoparticles induces polarized emission in perovskite nanocrystals, in contrast to the isotropic emission observed in samples without gold deposition.

Secondly, this dissertation explores the optical properties of quantum-confined one-dimensional (1D) cesium lead halide perovskite nanorods, with a specific focus on their anisotropic optical properties. Ensemble fluorescence anisotropy measurements of the nanorods reveal spectrally dependent anisotropy, characterized by a peak in anisotropy for band-edge excitation, indicating the influence of quantum confinement on the electronic structure.

Thirdly, this dissertation presents a strategy to determine the anisotropic complex dielectric function of CsPbBr3 nanorods by analyzing the ensemble absorption spectra in conjunction with the ensemble spectral fluorescence anisotropy. This strategy enables the differentiation of light absorption parallel and perpendicular to the main axis, facilitating the determination of the real and imaginary components of the dielectric function along each direction using an iterative matrix inversion (IMI) methodology. The resulting anisotropic dielectric function elucidates how the effects of quantum confinement on the electronic structure and the 1D shape anisotropy individually contribute to the optical properties of CsPbBr3 nanorods.