Deposition of nanocrystal thin films of Cu2Se and their optical and electrical characterization
TL;DR: In this paper, the structure of the films was analyzed using Grazing Incidence X-ray Diffraction (GIXRD) and High Resolution Transmission Electron Microscopy (HRTEM) analyses.
Abstract: Cu2Se nanocrystal (NC) films of different nanocrystal sizes were synthesized using vacuum deposition technique. The structure of the films was analyzed using Grazing Incidence X-ray Diffraction (GIXRD) and High Resolution Transmission Electron Microscopy (HRTEM) analyses. Band gaps of the films were found to decrease with increase in grain size. Analysis of the Raman spectra of the Cu2Se NC films showed that the exciton-phonon coupling in the films could be tuned by varying the grain size. DC conductivity of the films was found to increase and the activation energy for conduction to decrease with increase in the grain size of the samples. The grain size dependent conductivity along with the optical properties of the Cu2Se NC films may find practical applications such as window material for solar cells.
Citations
More filters
62 citations
TL;DR: The recent advances in the synthesis of size- and morphology tunable nanostructures by different methods; surface modification and functionalization for different purposes; and bioapplications for diagnosis and treatment of tumors by different imaging and therapy methods are summarized.
Abstract: Copper chalcogenides have a simple general formula, variable atomic ratios, and complicated crystal structures, which lead to their wealth of optical, electrical, and magnetic properties with great potential for wide applications ranging from energy conversion to the biomedical field. Herein, we summarize the recent advances in (1) the synthesis of size- and morphology tunable nanostructures by different methods; (2) surface modification and functionalization for different purposes; and (3) bioapplications for diagnosis and treatment of tumors by different imaging and therapy methods, as well as antibacterial applications. We also briefly discuss the future directions and challenges of copper chalcogenide nanoparticles in the biomedical field.
35 citations
TL;DR: In this article , the polypyrrole-encapsulated Cu 2 Se nanosheets in-situ grown on the Cu mesh (Cu 2 Se@PPy) act as a high-performance anode for sodium-ion batteries, capable of delivering a high specific capacity of 293.0 mAh g −1 at 1.0 A g − 1 , impressive rate capacity of 263.5 mAhg −1 under 10.0
Abstract: PPy-encapsulated Cu 2 Se nanosheets in-situ grown on the Cu mesh (Cu 2 Se@PPy) acts as a high-performance anode for sodium-ion batteries, capable of delivering a high specific capacity of 293.0 mAh g −1 at 1.0 A g −1 , impressive rate capacity of 263.5 mAh g −1 under 10.0 A g −1 over 2000 cycles. • Cu 2 Se nanosheets were in-situ grown on Cu mesh at room temperature. • PPy coating layer enables robust structure stability and fast charge transport. • Cu 2 Se@PPy as a SIBs anode gives high specific capacity. • Cu 2 Se@PPy as a SIBs anode offers outstanding cycling durability. Copper selenide (Cu 2 Se) features high theoretical capacity and quasi-2D characteristics built by repeating sextuple layers of Se-Cu-Cu-Cu-Cu-Se, making it a fascinating anode for sodium-ion batteries (SIBs). However, it experiences huge volume variation during repeated discharge–charge processes. Here, a productive approach to preserve the structure of Cu 2 Se anode via in-situ coating conductive polymer carbon is proposed. As a demonstration, Cu 2 Se nanosheets encapsulated by polypyrrole (PPy) were anchored on Cu mesh (Cu 2 Se@PPy) and regarded as an electrode material for SIBs. The PPy shell enjoys double functions that improves the electronic conductivity as well as alleviates the significant volume swelling of Cu 2 Se. As a result, Cu 2 Se@PPy gives a satisfactory electrochemical performance, including high specific capacity of 293.0 mAh g −1 at 1.0 A g −1 , impressive rate capacity (263.5 mAh g −1 under 10.0 A g −1 over 2000 cycles). This work describes the uncomplicated approaches available for designing high stability metal selenides anodes for sodium storage.
34 citations
TL;DR: In this paper, the influence of loading strain rate and composition on the creep compliance and retardation spectra of Ni-Zr binary alloys with three different compositions and degrees of crystallinity was investigated.
Abstract: Variation in composition of an alloy thin film can alter its microstructure, which provides control over its nanomechanical behavior. To explore this idea, we fabricate thin films of Ni-Zr binary alloys with three different compositions and degrees of crystallinity. At low Zr-content, the microstructure is nanocrystalline, which becomes a mixture of amorphous and nanocrystalline phases at intermediate Zr-content. Further, the increase in Zr-content yields a predominantly amorphous film. Nanoindentations of the films reveal negative strain rate sensitivities over the investigated range of composition, although the effect becomes more pronounced with an increase in the Zr-content. Furthermore, the experiments render a closer view of the nanoindentation creep deformation of these Ni-Zr thin films. In particular, we have examined the influence of loading strain rate and composition on the creep compliance and retardation spectra, which provide valuable insight into the timescales associated with the time-dependent relaxation mechanisms. While the decrease in crystallinity mitigates the creep resistance, an increase in the loading strain rate is found to give rise to fast relaxation mechanisms corresponding to relatively smaller timescales. This study also introduces and highlights the prospects of analyzing the instantaneous strain rate sensitivity measured during the nanoindentation creep, which shows temporal features qualitatively analogous to that of the retardation spectra.
10 citations
TL;DR: In this article, the authors used hydrothermal reactions and water-evaporation-induced self-assembly to synthesize Sb2Se3 and β-Cu2Se nanowires, respectively, with diameters of 100-200 nm and lengths of 2-3 μm.
Abstract: Hydrothermal reactions and water-evaporation-induced self-assembly were employed to synthesize Sb2Se3 and β-Cu2Se nanowires, respectively, with diameters of 100–200 nm and lengths of 2–3 μm. The resulting nanowires were subsequently characterized using XRD, XPS, FE-SEM, FE-TEM, and EDS elemental mapping to determine their physical, morphological, and chemical properties. Sb2Se3 nanowires exhibited low electrical conductivities and high Seebeck coefficients, whereas β-Cu2Se nanowires had high electrical conductivities and low Seebeck coefficients. Increasing the β-Cu2Se content in the mixtures containing Sb2Se3 and β-Cu2Se nanowires concomitantly enhanced the electrical conductivities but lowered the Seebeck coefficients. The nanowire sample with 30% β-Cu2Se and 70% Sb2Se3 exhibited maximal power factor and figure merit values of 389.19 μW m−1 K2 and 0.288, respectively, at 473 K.
9 citations
References
More filters
TL;DR: In this paper, the authors used a Geiger counter spectrometer to measure the changes in intensity distribution in the spectra of cold worked aluminium and wolfram and found that the line breadths may be attributed to simultaneous small particle size and strain broadening, the latter predominating at the higher Bragg angles.
Abstract: Methods of analysis previously used in the interpretation of line broadening are discussed and are shown to be inadequate; more reliable methods being outlined. An analysis of published results using one of these methods suggests that the observed effects can be attributed to simultaneous small particle size and strain broadening. Measurements of the changes in intensity distribution have been made, using a Geiger counter spectrometer, in the spectra of cold worked aluminium and wolfram. The line breadths may be attributed to simultaneous small particle size and strain broadening, the latter predominating, particularly at the higher Bragg angles, and it is shown that the observed effects are produced by dislocations or some similar structural fault. The observed rise in the breadths of the high angle lines from annealed materials suggests that some dislocations remain after annealing. Fourier analysis of the line shapes in general merely confirm the results of the analysis of the line breadths, but in the case of the recovered specimens it suggests that the dislocations form into walls (“polygonization”).
7,802 citations
TL;DR: This Review discusses some of the recent developments in the design and implementation of such photonic elements in thin-film photovoltaic cells, including nanoscale wires, particles and voids.
Abstract: High-performance photovoltaic cells use semiconductors to convert sunlight into clean electrical power, and transparent dielectrics or conductive oxides as antireflection coatings. A common feature of these materials is their high refractive index. Whereas high-index materials in a planar form tend to produce a strong, undesired reflection of sunlight, high-index nanostructures afford new ways to manipulate light at a subwavelength scale. For example, nanoscale wires, particles and voids support strong optical resonances that can enhance and effectively control light absorption and scattering processes. As such, they provide ideal building blocks for novel, broadband antireflection coatings, light-trapping layers and super-absorbing films. This Review discusses some of the recent developments in the design and implementation of such photonic elements in thin-film photovoltaic cells.
835 citations
TL;DR: In-depth characterization indicated that pure stoichiometric CZTS nanocrystals with an average particle size of 12.8 +/- 1.8 nm were formed, and optical measurements showed a band gap of 1.5 eV, which is optimal for a single-junction solar device.
Abstract: Recent advances have been made in thin-film solar cells using CdTe and CuIn1−xGaxSe2 (CIGS) nanoparticles, which have achieved impressive efficiencies. Despite these efficiencies, CdTe and CIGS are not amenable to large-scale production because of the cost and scarcity of Te, In, and Ga. Cu2ZnSnS4 (CZTS), however, is an emerging solar cell material that contains only earth-abundant elements and has a near-optimal direct band gap of 1.45−1.65 eV and a large absorption coefficient. Here we report the direct synthesis of CZTS nanocrystals using the hot-injection method. In-depth characterization indicated that pure stoichiometric CZTS nanocrystals with an average particle size of 12.8 ± 1.8 nm were formed. Optical measurements showed a band gap of 1.5 eV, which is optimal for a single-junction solar device.
581 citations
TL;DR: It is reported that the conductivity of thin films of n-type CdSe nanocrystals increases by many orders of magnitude as the occupation of the first two electronic shells, 1Se and 1Pe, increases, either by potassium or electrochemical doping.
Abstract: A bottleneck limiting the widespread application of semiconductor nanocrystal solids is their poor conductivity. We report that the conductivity of thin films of n-type CdSe nanocrystals increases by many orders of magnitude as the occupation of the first two electronic shells, 1Se and 1Pe, increases, either by potassium or electrochemical doping. Around half-filling of the 1Se shell, a peak in the conductivity is observed, indicating shell-to-shell transport. Introducing conjugated ligands between nanocrystals increases the conductivities of these states to approximately 10(-2) siemens per centimeter.
536 citations