Browsing by Author "Xu, Fan"
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Item Impact of Different Surface Ligands on the Optical Properties of PbS Quantum Dot Solids(MDPI (Multidisciplinary Digital Publishing Institute), 2015-04-21) Xu, Fan; Gerlein, Luis Felipe; Ma, Xin; Haughn, Chelsea R.; Doty, Matthew F.; Cloutier, Sylvain G.; Fan Xu, Luis Felipe Gerlein, Xin Ma, Chelsea R. Haughn, Matthew F. Doty and Sylvain G. Cloutier; Xu, Fan; Ma, Xin; Doty, Matthew F.; Cloutier, Sylvain G.The engineering of quantum dot solids with low defect concentrations and efficient carrier transport through a ligand strategy is crucial to achieve efficient quantum dot (QD) optoelectronic devices. Here, we study the consequences of various surface ligand treatments on the light emission properties of PbS quantum dot films using 1,3-benzenedithiol (1,3-BDT), 1,2-ethanedithiol (EDT), mercaptocarboxylic acids (MPA) and ammonium sulfide ((NH4)2S). We first investigate the influence of different ligand treatments on the inter-dot separation, which mainly determines the conductivity of the QD films. Then, through a combination of photoluminescence and transient photoluminescence characterization, we demonstrate that the radiative and non-radiative recombination mechanisms in the quantum dot films depend critically on the length and chemical structure of the surface ligands.Item Impact of Different Surface Ligands on the Optical Properties of PbS Quantum Dot Solids(MDPI AG, 2015-04-21) Xu, Fan; Gerlein, Luis Felipe; Ma, Xin; Haughn, Chelsea R.; Doty, Matthew F.; Cloutier, Sylvain G.; Fan Xu, Luis Felipe Gerlein, Xin Ma, Chelsea R. Haughn, Matthew F. Doty and Sylvain G. Cloutier; Xu, Fan; Ma, Xin; Haughn, Chelsea R.; Doty, Matthew F.; Cloutier, Sylvain G.The engineering of quantum dot solids with low defect concentrations and efficient carrier transport through a ligand strategy is crucial to achieve efficient quantum dot (QD) optoelectronic devices. Here, we study the consequences of various surface ligand treatments on the light emission properties of PbS quantum dot films using 1,3-benzenedithiol (1,3-BDT), 1,2-ethanedithiol (EDT), mercaptocarboxylic acids (MPA) and ammonium sulfide ((NH4)2S). We first investigate the influence of different ligand treatments on the inter-dot separation, which mainly determines the conductivity of the QD films. Then, through a combination of photoluminescence and transient photoluminescence characterization, we demonstrate that the radiative and non-radiative recombination mechanisms in the quantum dot films depend critically on the length and chemical structure of the surface ligands.Item The synthesis of PbS nanocrystal and their self-assembly into complex nanowire and nanocube structure(University of Delaware, 2011) Xu, FanFor the last 50 years, bulk lead-chalcogenide semiconductors have been key materials for infrared light sources and lasers, photodetectors and highperformance thermoelectrics. Meanwhile, the colloidal synthesis of chalcogenide semiconductor nanocrystals has provided a new pathway to producing optoelectronic materials with unique physical properties at low cost, including lead-chalcogenide nanocrystals. In this thesis, we synthesized various sizes of lead salt nancrystals that exhibit remarkable photoluminescence efficiencies across the near infrared region at room-temperature, which can be appealing active material for light emitting devices, photovoltaic devices, and bio-imaging. Meanwhile, we developed the catalyst-free self-attachment of PbS nanowires in hot colloidal solution using a combination of multiple surfactants. We demonstrate the controllable self-attachment of star-shaped nanocrystals can lead to radically-branched nanowires while the assembly of octahedral nanocrystals leads to zigzag nanowires. The synthesized nanowires exhibit strong position dependent quantum confinement, which occurs at the side arms and high faceted edges of the nanowires. Those novel structures give rise to the appealing optical properties of the nanowires, with strong photoluminescence in the near infrared region.