CuInSe2 Nanowires Research Articles

One-pot synthesis of branched CuInSe2 nanowires based on solution-liquid-solid method and their implementation in photovoltaic devices

Branched CuInSe2 nanowires (NWs) are successfully synthesized by one-pot method for making secondary bismuth nanoparticles to attach onto the CuInSe2 NWs stem for inducing the secondary branch growth by solution-liquid-solid (SLS). The branched CuInSe2 NWs were measured in order to reveal its viability for PV device fabrication and application for the light-absorbing material in solar cells.

Cation exchange synthesis of CuIn x Ga1-x Se2 nanowires and their implementation in photovoltaic devices.

CuInxGa1−xSe2 (CIGS) nanowires were synthesized for the first time through an in situ cation exchange reaction by using CuInSe2 (CIS) nanowires as a template material and Ga-OLA complexes as the Ga source. These CIGS nanowires maintain nearly the same morphology as CIS nanowires, and the Ga/In ratio can be controlled through adjusting the concentration of Ga-OLA complexes. The characteristics of adjustable band gap and highly effective light-absorbances have been achieved for these CIGS nanowires. The light-absorbing layer in photovoltaic devices (PVs) can be assembled by employing CIGS nanowires as a solar-energy material for enhancing the photovoltaic response. The highest power conversion efficiency of solar thin film semiconductors is more than 20%, achieved by the Cu(InxGa1−x)Se2 (CIGS) thin-film solar cells. Therefore, these CIGS nanowires have a great potential to be utilized as light absorber materials for high efficiency single nanowire solar cells and to generate bulk heterojunction devices.

Flexible anodized aluminum oxide membranes with customizable back contact materials

Anodized aluminum oxide (AAO) membranes were fabricated using flexible substrate/carrier material. This method facilitates the use of AAO templates with many different materials as substrates that are otherwise incompatible with most anodization techniques. Thin titanium (Ti) and tungsten (W) layers were employed as interlayer materials. Titanium enhances adhesion. Tungsten not only helps eliminate the barrier layer but also plays a critical role in enabling the use of flexible substrates. The resulting flexible templates provide new, exciting opportunities in photovoltaic and other device applications. CuInSe2 nanowires were electrochemically deposited into porous AAO templates with molybdenum (Mo) as the back contact material. The feasibility of using any material to form a contact with semiconductor nanowires has been demonstrated for the first time enabling new avenues in photovoltaic applications.

Study of Electronic and Optical Properties of CuInSe2 Nanowires

The electronic and optical properties of the CuInSe2 nanowires have been investigated via density functional theory. We have used numerical atomic orbital bases set with local-density approximation. The norm-conserving pseudopotentials of Troullier and Martins have been used. In our calculation we used nanowires in two shapes of hexagonal and triangular with their diameters ranging from 8 to 15 A in the (1–10) growth direction. The geometrical parameters are in good agreement compared with other experimental or theoretical results. We show that for the nanowires there is a significant contraction of the Cu–Se and In–Se bond lengths at the edge of the wires (4.7%); as for the wires at the center, it is 2.6%. Moreover, we have investigated the band structures and atom-projected density of states of the nanowires. These studies confirm that CuInSe2 nanowires are semiconductors with a direct band gap. These studies also show the existence of hybridization between Cu-d with Se-p states in the middle valence su...

Synthesis and formation mechanism of CuInSe2nanowires by one-step self-catalysed evaporation growth

High-quality CuInSe2 (CISe) nanowires have been prepared by a one-step evaporation process. The presented growth process results in a composite material consisting of CISe NWs on top of a polycrystalline CISe base layer. The nanowires were extensively characterized by transmission electron microscopy, confirming their composition and atomic-scale crystal structure with a very low number of structural defects. From these analyses, we infer that the growth axis is along the [111] direction. The polycrystalline base layer has a tetragonal chalcopyrite structure and is optically active as confirmed by X-ray diffraction and photoluminescence (PL) analysis, respectively. Potential applications of this composite CISe NW/base-layer material for photovoltaic energy conversion are supported by the reduced reflectivity of the material and its strong PL intensity. The presented growth method is based on elemental evaporation under vacuum conditions, which makes the process compatible with the fabrication of photovoltaic devices.

Nanostructured CuInSe2 by electrodeposition with the assistance of porous silicon templates

In this work, the results of the electrodeposition and characterization of CuInSe2 nanowires with the assistance of porous silicon (PSi) templates are presented. Work was done first to obtain the appropriated conditions to prepare porous silicon layers with 70% of porosity, a pore diameter with average size ∼20–30 nm and thicknesses close to 2.5 μm by electrochemical etching of p-type (100) c-Si wafers. Then, PS layers were peeled-off from the c-Si wafer and transferred to glass/TCO substrates to fabricate the new glass/TCO/PS template substrates. Afterward, the electrodeposition of CuInSe2 into the PS templates was carried out using an acidic aqueous buffered bath that contained the three active ionic species. The deposition conditions to obtain nanostructured CuInSe2 on the PS templates were established after performing a systematic study of deposition parameters. SEM images, EDS and Raman results showed that nanostructured CuInSe2 was formed into porous silicon templates; the infiltration was verified using the Fast Fourier Transform of optical reflectance response for the samples before and after the CuInSe2 infiltration.

Characteristics of CuInSe2 Nanowire Arrays Electrodeposited into Anodic Alumina Templates with Dimethyl Sulfoxide (DMSO) Additive

We successfully fabricated ternary CuInSe2 nanowire arrays in a novel acidic Dimethyl sulfoxide (DMSO)-aqueous electrolyte using pulse electrodeposition techniques with the assistance of an anodized aluminum oxide (AAO) template and investigated the effects of deposition potential and a DMSO additive on the composition and crystallization of CuInSe2 nanowires. We obtained the near-stoichiometric CuInSe2 nanowires by tuning the deposition potential at −1.0 V. The addition of DMSO into the electrolyte significantly affects the pore-filling ratio and the growth rate of CuInSe2 nanowires. The detailed microstructure of CuInSe2 nanowires were obtained from the transmission electron microscopy (TEM) analysis, which shows the polycrystalline nature of CuInSe2 nanowires regardless of the electrolyte with and without DMSO. Proposed mechanism for the growth mechanism of nanowires deposited in the electrolyte with DMSO was presented on the basis of kinetic and thermodynamic process. Photoelectrochemical (PEC) characterizations showed that the CuInSe2 nanowires deposited in the electrolyte containing 0.5 mM DMSO exhibited a superior photocurrent response than the CuInSe2 nanowires deposited in the electrolyte without DMSO.

Solution−Liquid−Solid Synthesis of CuInSe2 Nanowires and Their Implementation in Photovoltaic Devices

CuInSe₂ (CIS) nanowires were synthesized by solution-liquid-solid (SLS) growth in a high boiling solvent using bismuth nanocrystals as seeds. The nanowires tended to be slightly deficient in In and exhibited either cubic or hexagonal crystal structure, depending on the synthesis conditions. The hexagonal structure, which is not observed in bulk crystals, appears to evolve from large concentrations of twin defects. The nanowires could be compressed into a free-standing fabric or paper-like material. Photovoltaic devices (PVs) were fabricated using the nanowires as the light-absorbing layer to test their viability as a solar cell material and were found to exhibit measurable PV response.

Synthesis and formation mechanism of helical single-crystalline CuInSe2 nanowires

Highly ordered single-crystalline CuInSe2 nanowires array have been prepared via a facile solution approach by using anodic aluminium oxide (AAO) as a hard template. CuInSe2 nanowires with a novel helical shape are found to be formed by this approach. A screw-dislocation-induced growth process is proposed for the formation mechanism of this interesting nanostructure based on detailed structural characterizations. The CuInSe2 helical nanowires have an average diameter of 200 nm and a periodicity of about 50–100 nm. Another type of CuInSe2 nanowire with a straight shape is also found in the product and an oriented attachment mechanism has been used to explain its growth. Nanowires with both types of shapes have the same [112] growth direction. The structure, morphology, composition and optical absorption properties of the as-prepared samples were characterized using X-ray powder diffraction, transmission electron microscopy, energy dispersive X-ray spectrometry, scanning electron microscopy and UV-Vis spectrophotometry.

Surfactant effect on the formation of CuInSe2 nanowires in solution phase synthesis

Solution-phase synthesis of CuInSe2 nanowires without using metal nanocrystal catalysts has been demonstrated. The morphology of chalcopyrite CuInSe2 nanoparticles could be varied from spheres to highly anisotropic nanowires by varying the relative amount of strong and weak binding surfactants passivating the surface. For CuInSe2 nanowires, weakly binding dioctylphosphine oxide (DOPO) was found to be the key surfactant that enables the anisotropic 1-dimensional growth. Detailed analysis of the structure of the nanowires indicates that they grow perpendicular to (112) planes, with twinning around the growth axis by ∼60° rotation. The nanowires of CuInSe2 synthesized in this study exhibit saw-tooth surface morphology resembling a stack of truncated tetrahedra which show a continuous growth mechanism.

Large-Scale Synthesis and Phase Transformation of CuSe, CuInSe2, and CuInSe2/CuInS2 Core/Shell Nanowire Bundles

Facile chemical approaches for the controllable synthesis of CuSe, CuInSe2 nanowire, and CuInSe2/CuInS2 core/shell nanocable bundles were developed. Hexagonal CuSe nanowire bundles with lengths up to hundreds of micrometers, consisting of many aligned nanowires with a diameter of about 10-15 nm, were prepared by reacting cubic Cu(2-x)Se nanowire bundles with a sodium citrate solution at room temperature. The CuSe nanowire bundles were then used as self-sacrificial templates for making bundles of tetragonal chalcopyrite CuInSe2 nanowires by reacting with InCl3 via a solvothermal process. Furthermore, bundles of CuInSe2/CuInS2 core/shell nanocables were obtained by adding sulfur to the reaction system, and the shell thickness of the polycrystalline CuInS2 in the nanocables increased with increasing S/Se molar ratios. It was found that the small radius of copper ions allows their fast outward diffusion from the interior to the surface of nanowires to react with sulfur atoms/anions and indium ions to form a CuInS2 shell. Enhanced optical absorption in the vis-NIR region of CuInSe2/CuInS2 core/shell nanocable bundles is demonstrated, which is considered beneficial for applications in optoelectronic devices and solar energy conversion.

Fabrication of ordered single-crystalline CuInSe2 nanowire arrays

Chalcopyrite CuInSe2 nanowire arrays have been prepared via a convenient one-step solution approach using porous anodic aluminium oxide (AAO) as a hard template. The as-prepared highly oriented CuInSe2 nanowires are uniform and single crystalline with a [112] growth direction. The diameter of the CuInSe2 nanowires is tunable and determined by the pore size in the AAO template. The structure, morphology, composition and optical absorption properties of the as-prepared CuInSe2 samples were characterized using X-ray powder diffraction, transmission electron microscopy, energy dispersive X-ray spectrometry, scanning electron microscopy and UV–Vis spectroscopy. A possible formation mechanism of the CuInS2 arrays is proposed. Homogeneous nucleation is believed to occur within AAO pores during the reaction and lead to the formation of single crystalline CuInSe2 nanowires.

CuInSe2 Nanowires as New Solar Cell Materials

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Synthesis and Phase Transformation of In2Se3 and CuInSe2 Nanowires

III−VI and I−III−VI semiconductors with anomalous grain boundaries have been actively studied for high efficiency photovoltaic applications. Nanowire morphology can provide a well-defined nanodomain for studying grain boundary and p−n junction physics for improving solar cell efficiency. We report the synthesis of In2Se3 and CuInSe2 single crystalline nanowires via a Au-catalyzed vapor−liquid−solid growth. Superlattice forms in In2Se3 nanowires at room temperature and a reversible superlattice transformation takes place at 200 °C. Cu concentration in CuInSe2 nanowires can be controlled, and nanowires show a dependence of crystal structure on Cu concentration.