Date of Award
Doctor of Philosophy (PhD)
Perovskites are a group of crystalline chemicals with ABX3 formula where cations are surrounded by corner-sharing octahedra. Their crystal structure was described by Victor Goldschmidt in 1926, almost a century after the first discovery of the mineral perovskite, CaTiO3, by Gustav Rose in 1839. Organic-inorganic (hybrid) lead halide perovskites became a point of interest when their potential as a visible-light adsorber in solar cells was demonstrated by Kojima et. al. in 2009. All-inorganic perovskites gain traction after their synthesis as colloidal quantum dots in 2014. While there have been numerous studies on the application of perovskite nanoparticles (NP) in optoelectronic devices, lasers and sensors, there is a lot of chemistry to explore to reach their full potential. The focus of this dissertation is on all-inorganic CsPbX3 nanoparticles. In chapter two, a novel microwave assisted method is described to synthesize 2-dimentional (2D) CsPbX3 NPs in benzyl ether. We demonstrated that microwave irradiation provides a feasible and reproducible path to tailor the morphology of these NPs. Then, the NP’s structural features and subsequent optoelectronic properties are explained. To fully understand the effect of the structure and composition on the band gap of these NPs, a comprehensive description of the intrinsic optoelectronic properties of CsPbX3 NPs is reported in chapter one. To elucidate their synthesis path further, we compared them with NPs prepared with a stablished synthesis technique, hot-injection method in 1-octadecene, in chapter three. This comparison shed light on the preference of the NPs to grow in 2D directions in benzyl ether under microwave irradiation. This study was expanded, by monitoring the growth of CsPbBr3 NPs over time at ambient condition as well, which confirmed the role of benzyl ether in the morphology. Other perovskite synthetic methods are also reviewed in chapter one, along with the various mechanisms of orientational growth in CsPbX3 NPs. In addition, we explored the effect of benzyl ether on ionic interactions in the lead halide precursor, in particular, the formation of halo plumbate complexes and their contribution in the 2D growth of the perovskite colloidal seeds were evaluated. In chapter four, the goal was to use a halide exchange technique to stabilize CsPbI3 NPs in colloidal form and in thin film format. In this chapter, the electronic band gap of the CsPbBr3 and I-rich CsPbX3 NPs was measured using cyclic voltammetry. We calculated the energy gap between HOMO and LUMO of the NPs and explain the contribution of atomic orbitals, as well.During this dissertation research, we sought to learn the chemistry of all-inorganic perovskites and became fascinated with their adaptability to the synthesis environment and their dynamic response to the post-synthesis challenges. This ability provides tremendous opportunity for researchers to tailor perovskite NPs for applications that require a semiconductor with any desired band gap that can be formed into nano-, micro- or macro-scale with flexibility.
Zamani, Hediyeh, "CsPbX3 Nanoparticle Synthesis Via Nonpolar Solvent Choice and Microwave Heating, Growth Mechanism and CsPb(Br/I)3 Stabilization by Halide Exchange" (2023). Dissertations - ALL. 1702.