Research On Optical Properties Of Metal-Perovskite Quantum Dots Composite Nanostructures

The emission of optical materials can be enhanced and their radiation can be amplified by coupling with novel metal nanoparticles with localized surface plasmon resonance?LSPR?effect in the metal-quantum dots composite nanostructures.The perovskite CsPbX₃?X=Cl/Br/I?quantum dots?QDs?have received more and more attention due to their high photoluminescence quantum yield?PLQY?,large absorption cross section,tunable emission band,etc.These novel QDs were expected to apply to such fields as bio-probes,light-emitting diodes?LEDs?,nanolasers and solar cells.In this dissertation,metal-perovskite QDs composite nanostructures?MPQD-CNs?were studied.Firstly,based on relevant theory research,the electric field mode distribution was clarified by theoretically simulating the MPQD-CNs.Then,after series of experiments,improved synthetic process was proposed to prepare CsPbX₃nanocrystals and accurately control their morphologies and emission bands.On this basis,the MPQD-CNs were also prepared with both the enhanced photoluminescence intensity and improved stability in relation to humidity,compared with pure CsPbX₃nanocrystals.Finally,with applied research,the CsPbX₃ nanocrystals were applied as gain materials for plasmonic nanolasers.The main works and innovation of this dissertation can be summarized as follows:1)LSPR effects with three different types of MPQD-CNs were numerically analyzed to study the theoretical mechanism of optical physics.Firstly,the numerical results showed that the CsPbBr₃@Ag composite nanostructure can contribute to a 35-fold electric field enahncement around the Ag nanoparticles under the irradiation of 400nm incident light based on the finite element method?FEM?analysis.Then,FEM analysis was performed on the Au@SiOx:CsPbBr₃ structure.The numerical results also found that an efficient exciton-LSPs coupling can be obtained by spatially high-degree overlappling between CsPbBr₃ QDs and the LSPRs of Au core.Finally,a three-layer?i.e.,gain media-silver-gain media?nanoshell-based plasmonic laser was proposed with a super low threshold.The optical cross-sections with different gain levels were calculated to analyze the gain thresholds of the proposed plasmonic lasers with different plasmonic modes.The results indicated that an 87%reduction of the gain threshold of the plasmonic laser can be obtained with a quadrupole mode.With the appropriate optimal parameters obtained,we successfully designed a novel plasmonic nanolaser with an extremely low threshold.2)A novel synthetic process of CsPbX₃ nanocrystals was successfully developed in open air.The PLQY of CsPbX₃ nanocrystals was up to 90%and the emission bands could be tuned in the visible region with narrow width from 10 to 40 nm.The CsPbX₃@Ag composite nanocrystals were prepared by depositing the Ag nanoparticles on the surface of CsPbX₃ nanocrystals,and the emission intensity was significantly enhanced compared with the pure CsPbX₃ nanocrystals.It was found that the Ag nanoparticles facilitated the absorption of UV light around 400 nm in CsPbX₃ nanocrystals,which resulted in the enhanced emission intensity,although the PLQY was slightly reduced.3)A plasmonic nanolaser via embedding perovskite QDs in rationally designed dual-mesoporous silica nanocomposites with gold nanocore?denoted as DMS?was demonstrated.Its mechanism was elaborated.The threshold was 1.08 mJ/cm².The full-width at half-maximum?FWHM?was 4.5 nm.On the one hand,the novel DMS were helpful for the template-assisted formation of perovskite QDs.On the other hand,they also contributed to the distance control between the gold nanocore and perovskite quantum dots,with results in both an efficient dynamic exciton-plasmon coupling,and a robust protective layer of perovskite QDs to improve their water stability.In addition,the same structure could also effectively inhibit the ion exchange effect between CsPbX₃ nanocrystals with different composition.