Papers by Keyword: PbSe

Abstract: Colloidal syntheses of PbSe nanocrystals (NCs) have been widely investigated and the properties of nanocrystals have been shown to vary with reaction conditions, time, concentration and chemistry of reagents as well as the surfactants used. In this work the effects of reaction temperature, solvents, ligand purity, lead and selenium sources on the optical and structural properties of PbSe nanocrystals were investigated. PbSe NCs synthesized at 90 °C were observed to be spherical and had a narrower size distribution as compared to those synthesized at higher temperatures. 1-octadecene, trioctylphosphine and oleylamine were investigated as solvents for NC synthesis with the non-coordinating solvent octadecene showing the fastest growth rate with medium sized NCs. The coordinating solvents trioctylphosphine and oleylamine produced larger and smaller NCs respectively; this could be attributed to solvent interference during NC nucleation and growth phases. Oleate ligands were used during these syntheses and the ligand purity was not observed to have a significant effect on the NC optical and structural properties. The selenium precursor used affected the NC size and their optical properties while the lead source influenced both the NC shape and size. Lead acetate produced cubic NCs which were larger than the spherical NCs obtained when lead oxide was used.

Abstract: This essay employed the "successive ion layer adsorption and reaction (SILAR)"technology to form PbSe/CdSe core/shell.We use the Pbse/CdSe core/shell replaced PbSe nanocrystals and obtained one new quantum dot solar cells of the inorganic.This new solar cells constituted by the metal oxide films retain the photoelectric conversion efficiency of quantum dot solar cells.At the same time,the stability of the new solar cells is tremendously improved with the oxidation resistance of inorganic oxide.Finally,when J_sc=25.2mA/cm²and V_oc=0.36V ,we can conclude the conversion efficiency of the solar cell can be evaluated as 3.929%.

Abstract: We here report the temperature effect on photoluminescence(PL) spectra of PbSe quantum dots (QDs), which exhibit a strong temperature dependence on their spectra position and intensity. They potentially act as the temperature marker, sensing temperature variations and reporting temperature changes remotely through optical readout. In addition, the temperature sensitivity characterized by peak position of PbSe QDs was found to be 0.39nm/°C in a range of 10-100 °C.

Abstract: The effects of composition on the performance of hybrid photovoltaic cells based on PbSe nanocrystal quantum dot(NQD)/ poly(3-hexylthiophene) nanocomposites were studied. The device performance and the absorption property strongly depended on the loading of PbSe. To improve the device performance, a pure light-absorbing P3HT film was inserted underneath the blended layer of P3HT and PbSe nanocrystal quantum dots in the active region. Such a design allowed for the employment of a thinner bulk heterojunction for more efficient carrier collection without an excessive reduction of the overall light absorption by the photovoltaic cell. The measured device performance showed a significant improvement over previously reported hybrid cells containing bulk heterojunctions of P3HT and Pb(S,Se) nanocrystal quantum dots.

Abstract: Lead selenide (PbSe) is quite an important semiconductor material with several superior physical properties, e.g. optical and electrical ones. In this paper, PbSe nanocrystals (NCs) with different morphologies such as sphere, rod and hexagon were successfully prepared by an ultrasonic electrochemical method, using sodium citrate as the coordination agent, at room temperature. The crystal structure and the morphology of the as-prepared PbSe NCs were confirmed by means of the Transmission Electron Microscopy (TEM) and X-ray diffractometer (XRD). The ultraviolet-visible Spectrophotometer (UV) was performed to analyze the optical properties of the PbSe NCs. Results show that the nanospheres were about 60 nm in diameter, and the nanorods were 20 nm in diameter with a slenderness ratio of 25. The possible mechanism for the nanorods growth was discussed. The energy gap of the PbSe NCs deduced from the UV-visible spectra was much larger than their bulk counterparts, due to the quantum size effect.

Abstract: Synthesis of intermetallic PbSe induced by high-energy ball milling has been studied. Systematic analysis of transformation in the resulting phases of milling from 0 to 10 h has been traced by characterizing the microstructures in terms of morphology, crystallite size, and percentages of phases formed as a function of milling time. Results reveal the formation of two phases. Where the system of PbO-Se transforms gradually to PbSe. Complete transformation is achieved after 10 h of milling time. Study of particle structure by the Rietveld Method further corroborates the value of the nano-order crystallite diameters as evaluated from the microscopic studies.

Abstract: With the assistance of diethylenetriamine(DETA), well-crystalline PbSe cuboidal structures with different concave faces in each plane have been successfully prepared through a hydrothermal process using Na2SeO3 as selenium source at 180 °C for 48 h. The products have been characterized by means of X-ray diffraction, field-emission scanning electron microscopy and luminescence spectroscopy. The field emission scanning electron microscopy showed that the edge lengths of these cuboidal crystals ranged from 1.5 to 2.5 µm, and the edges of a cube crystal extend outwards from its core with a tiny cubic center leaving step-like faces. The shape evolution of PbSe crystal from eight-dendritic structure to cuboidal structure was observed and the possible growth mechanism was proposed. Results revealed that the temperature played a crucial role in the final morphology of PbSe microstructures, and other factors such as the solvent composition and the molar ratio of metal/chalcogen were also discussed. The photoluminescence (PL) spectrum of as-prepared PbSe crystals shows the photoluminescence emission spectrum consists of a main intense peak at 435 nm and a shoulder at 420 nm. This synthesis method could be extended to the morphogenesis of other inorganic crystals with complex forms.

Abstract: The synthesis of high-quality monodispersed nanocrystal is very important. Typical synthetic method is rapid nucleation by injection of an organometallic precursor into a solvent maintaining the reaction temperature. Since these methods are discontinuous processes, they are not efficient for large-scale production of monodisperse nanocrystals. In this study, continuous microchannel reaction technique is presented for synthesis of monodisperse lead selenide nanocrystals in a diphenyl ether as high-temperature organic media. The microchannel reactor was used due to its possibility of continuous process and reproducibility of narrow size distribution in nanocrystal synthesis. The synthesis was carried out in microchannel reactor (800 μm diameter) made from PTFE. Lead oleate and TOP-Se were used as organic precursor and diphenyl ether as high-temperature organic solvents. Lead selenide particles with a size of less than 10nm could be continuously prepared by this method. The nanocrystals have been characterized by X-ray diffraction, TEM and optical absorption spectrometer.