Author ORCID Identifier

https://orcid.org/0009-0000-9672-7973

Date Available

7-20-2025

Year of Publication

2025

Document Type

Doctoral Dissertation

Degree Name

Doctor of Philosophy (PhD)

College

Engineering

Department/School/Program

Mechanical Engineering

Faculty

Dr. Wei Li

Faculty

Dr. Fuqian Yang

Abstract

Cesium lead bromide (CsPbBr3) perovskite nanocrystals (NCs) have garnered significant interest due to their exceptional optoelectronic properties, including high photoluminescence quantum yield, tunable bandgap, and excellent carrier dynamics. These attributes make them promising candidates for applications in light-emitting diodes, photovoltaics, and sensing technologies. However, optimizing their synthesis and improving their environmental stability remain critical challenges. This dissertation explores the growth kinetics of CsPbBr3 NCs, focusing on the effects of stirring speed and water exposure on their structural and optical properties.

The synthesis of CsPbBr3 NCs was performed using both mechanochemical (MC) and antisolvent methods, enabling an in-depth investigation of growth mechanisms under dynamic conditions. The impact of stirring speed on crystal formation was systematically analyzed by monitoring photoluminescence (PL) peak evolution, X-ray diffraction (XRD) patterns, and transmission electron microscopy (TEM) imaging. Increasing the stirring speed led to reduced crystal size and increased nominal activation energy, as confirmed by Stokes shift analysis and Tauc plot calculations. These findings highlight the role of shear stress in modulating monomer migration and nucleation rates, affecting the quantum confinement effect observed in CsPbBr3 NCs.

To assess environmental stability, the interaction of CsPbBr3 NCs with water was evaluated using poly(methyl methacrylate) (PMMA) encapsulation. PL intensity degradation studies revealed that unprotected CsPbBr3 NCs undergo rapid decomposition upon water exposure, leading to a shift in emission wavelength and reduced stability. Conversely, PMMA-CsPbBr3 films exhibited enhanced resistance to water-induced degradation, with a significantly lower diffusion coefficient (1.70 × 10⁻¹² m²/s) for water molecules within the polymer matrix. Thermal activation energy analysis further demonstrated that encapsulation increases the energy barrier for degradation, thereby improving long-term stability.

The results of this study provide valuable insights into the kinetic control of CsPbBr3 NC growth and their stability in aqueous environments. By optimizing synthesis parameters and employing protective encapsulation strategies, this research paves the way for the development of more durable and scalable perovskite-based optoelectronic devices. Future work may extend these findings to other perovskite compositions and hybrid material systems for enhanced performance and environmental resilience.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2025.263

Funding Information

This study was supported by the NSF (National Science Foundation) Grant (CBET-2018411) in 2022.

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