"高分子/鈣鈦礦複合材料：奈米粒子生長, 結構分析和電子以及光電應用"

Abstract

Organic-inorganic hybrid perovskite (OIHP) materials have been intensively studied in recent years due to their superior electronic and optical properties. Although, the material possesses such fascinating properties, there are significant limitations and challenges that affect device performance as well as mechanical and ambient stability. To overcome such disadvantages, one of the mostly adopted approach is the formation of the perovskite/polymer composite materials that can possess both perovskite and polymer properties. The work outlined herein particularly concerns OIHP nanoparticles (NPs) formation within the polymeric matrixes by taking advantages of chemical interactions between OIHP and polymers. In this thesis, the main idea is to study size control of OIHP nanocrystals and morphology of OIHP/polymer composites indicating the importance in different devices for data storage and light emitting applications. Two different solution based approaches will be presented to form film and nanofiber based OIHP NP/polymer composites. The details of each topic are summarized as below: In chapter 2, OIHP (CH3NH3PbBr3) NPs was formed and well dispersed in an insulating solid polymer electrolyte (poly(ethylene oxide) (PEO)) benefiting the interaction between polymer and OIHP. It was revealed that PEO could serve as the chelating agent to coordinate with PbBr2/CH3NH3PbBr3 NPs in consequence of the direct interaction between Pb2+ cations and electron pairs of ether oxygen on the PEO chain to provide a host medium for the Pb2+ cations on both amorphous and crystalline phases. Herein, PEO was chosen not only to perform a matrix function due to formation of OIHP nanocrystals and PEO’s ionic conductivity but also to support a preservative material surrounding the OIHP NPs to improve their stability. Consequently, memory fabricated using this composite layer was showed resistive switching characteristic due to metallic filament formation in the derived device, leading to the write-once-read-many times resistive switching behavior. In chapter 3, the OIHP (CH3NH3PbBr3) NP was growth in four different host polymers as polystyrene (PS), poly(4-vinylphenol) (PVPh), poly(methyl methacrylate) (PMMA), and poly(methacrylic acid) (PMAA). Existed dissimilar chemical interaction between the host polymers and perovskite was studied resulting in different OIHP NP size distribution and composite morphology. Each composite layer was utilized for a novel photomemory device showing distinct photo-response and memory behavior attributing to the different morphologies of the hybrid dielectric layers and the different sizes of the distributed OIHP NPs. In chapter 4, co-axial (core-shell) electrospinning method was utilized to form OIHP NPs within thermoplastic polyurethane (TPU) nanofiber. Thanks to the existing chemical affinity between OIHP and TPU, NPs were well conserved and NP size distribution was limited by controlling solution parameters such as precursor composition, shell concentration as well as working conditions such as core-flow rate. Multi-color luminous OIHP nanofiber mats were achieved by changing the composition of OIHP precursor. Beside, hydrophobic TPU shell enhance mechanical stability of prepared fiber mats up to 100%-stretched state and it supports the ambient stability to the OIHP NPs up to one month. Lastly, intrinsic white light emitting nanofibers and white light emitting diode (LED) was demonstrated by taking advantage of energy transfer between OIHP NPs and conjugated polymers utilized in system.