Date of Award

Summer 8-27-2021

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor(s)

Zheng, Weiwei

Second Advisor

Qiao, Quinn

Keywords

Metal dichalcogenides, Nanomaterials, Perovskites, Two-dimensional

Subject Categories

Chemistry | Engineering | Inorganic Chemistry | Nanoscience and Nanotechnology | Physical Sciences and Mathematics

Abstract

Anisotropic nanocrystals (NCs) have become of keen interest in recent years, especially for applications in optoelectronic devices due to their directionally oriented emissions, narrow emission spectra, and suitable morphologies for device integration. Of the desired anisotropic NCs, two-dimensional (2D) NCs are of profound interest, due to their impressive optical and electronic properties as well as their prospective advantages towards applications in layered optoelectronic devices, such as solar cells. However, 2D NCs face many challenges, including limited synthetic derivation, as well as decreased stability and optical response, due to their large surface-to-volume ratio and reactive planar surface increasing surface defect state formation or reactions with possible antagonistic substances, such as moisture or oxygen. Additionally, their large lateral surface area makes dopant incorporation difficult, limiting discrete composition control. This is because their rapid NC formation mechanism makes self-purification of possible dopant impurities likely and their higher surface area makes surface adsorption of dopants more favorable. Therefore, simplified synthetic methods for doped 2D anisotropic NCs are still necessary, especially involving methods for improved environmental stability and optical activity. This work aims to provide methods in solution to these issues by developing simplified syntheses for 2D NCs and for shell passivation, with means of dopant incorporation and further synthetic manipulation. Specifically, three methods for the synthesis of 2D NCs were developed, one for II-VI group CdS nanoplatelets (NPLs) following a one-pot heat up approach, and two for all-inorganic cesium lead halide perovskite NPLs and nanosheets (NSs), with one by the post-synthetic solvothermal treatment of perovskite nanorods (NRs) and one by a ligand-mediated room temperature synthesis. Additionally, Mn2+-dopant incorporation methods were developed for each synthetic method and a novel low-temperature ZnS shell passivation method was developed for the production of Mn:CdS/ZnS core/shell NPLs to avoid NPL degradation during shell passivation. The physical, optical, and magnetic properties of the resulting doped systems were explored for prospective applications in optoelectronic devices.

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