Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | Department of Applied Physics | en_US |
| dc.contributor.advisor | Li, Mingjie (AP) | en_US |
| dc.creator | Ren, Hui | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/14555 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | en_US |
| dc.rights | All rights reserved | en_US |
| dc.title | Synthesis and spintronic applications of chiral perovskite nanomaterials | en_US |
| dcterms.abstract | Organic-inorganic perovskite materials have garnered significant research interest owing to their unique properties, such as long diffusion length, tunable bandgaps, and high absorption coefficients, which are advantageous in optoelectronics and photovoltaics. Concomitantly, the synthesis of various perovskite nanomaterials (i.e. <100 nm) including nanocrystals, nanoplates, nanosheets, nanowires, etc., has expanded the compositional diversity of the perovskites. The quantum confinement effect in these perovskite nanomaterials allows for tunable optical and electrical properties, enhancing their potential in optoelectronics applications. | en_US |
| dcterms.abstract | Recently, the introduction of chirality into perovskite structures, combined with their diverse optoelectronic properties, has extended their potential applications to chiral optoelectronics, ferroelectricity, spintronics, etc. Additionally, the finding of the spin-orbit coupling (SOC), Rashba splitting and long spin lifetimes in perovskites has opened new avenues for spintronic applications, which are crucial for advancing information technology and quantum computing constructs. | en_US |
| dcterms.abstract | Achieving long-lived spin orientation at room temperature without a magnetic field is highly desirable for spintronics applications. The chirality-induced spin selectivity (CISS) effect offers a promising approach for efficient spin generation and manipulation. This dissertation first investigates the spin generation, dynamics, and transport properties of newly developed colloidal chiral CsPbBr₃ nanocrystal platelets (NPLs) with varying well thicknesses. These chiral NPLs exhibit an extended spin depolarization lifetime of approximately 210 ps, around one order of magnitude longer than their nanocrystal counterparts. Notably, they also demonstrate high circularly polarized emission (5.0%), spin current polarization up to approximately 43%, and a spin diffusion length reaching 33 nm. Theoretical calculations indicate that the introduction of chiral ligands induces asymmetry in CsPbBr₃ NPLs, creating an additional barrier to spin flipping due to the distinct momentum troughs associated with different spin states. These findings provide valuable insights into the underlying mechanisms and highlight a novel class of materials with significant potential for future spintronic applications. | en_US |
| dcterms.abstract | Moreover, lead-free perovskite materials are promising alternatives to conventional lead-based perovskites due to their reduced toxicity and increased environmental stability. Despite the current focus on chiral perovskite thin films and single crystals, research on the chiral properties of lead-free double perovskite nanocrystals is limited. We successfully synthesized cubic phase Cs2AgInxBi1-xCl6 (x = 0, 0.3, 0.6, and 0.9) nanocrystals (NCs) using the hot injection method. The intrinsic chirality of Cs2AgIn0.9Bi0.1Cl6 NCs was observed while we studied the chiral signals induced by chiral molecules in perovskite nanocrystals. HADDF-STEM imaging and simulation confirmed chiral defects, specifically screw dislocations in Cs2AgIn0.9Bi0.1Cl6 NCs. Under the measurement of the circularly polarized transient absorption spectrum, both untreated and chiral ligand-treated Cs2AgI0.9Bi0.1Cl6 NCs exhibited remarkably long spin depolarization lifetime, spanning 10 ns. Additionally, we also investigated the degree of spin-polarized current under dark conditions in R-/S-MBA-treated Cs2AgIn0.9Bi0.1Cl6 NCs devices, induced by the chiral-induced spin selectivity (CISS) effect. Most importantly, we provide further proof of the CISS effect in spin photovoltaic devices with the measurement of the spin-polarized photocurrent at 0V under different directions of the magnet field. These findings enhance our understanding of the chiral properties and mechanisms of lead-free double perovskite nanocrystals and have significant implications for the design and development of spintronic applications based on these chiral perovskite nanomaterials. | en_US |
| dcterms.extent | xiii, 102 pages : color illustrations | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 2025 | en_US |
| dcterms.educationalLevel | Ph.D. | en_US |
| dcterms.educationalLevel | All Doctorate | en_US |
| dcterms.accessRights | open access | en_US |
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