415 research outputs found
ONE STEP ELECTRODEPOSITION OF CuInSe2 THIN FILMS
Formation of CuInSe2 (CIS) thin films from aqueous solution containing citrate as complexing agent is reported. The surface morphology and the composition of the deposited films are characterized by scanning electron microscopy (SEM). The texture of the deposits and their compositions are analyzed by X-ray diffraction and transmission electron microscopy (TEM). Annealing of the films at 350°C in flowing argon electrodeposited at potentials in the range [-0.24, -0.4 (V vs Ag/AgCl)] resulted in the formation of alpha-Cu 2 Se (JCPDS 24-1131) and CuSe (JCPDS 6-0427). On the contrary, annealing in the same conditions of the films electrodeposited between -0.4 and -0.6 V vs Ag/AgCl led to the formation of chalcopyrite CuInSe 2 (JCPDS 23-209) with alpha-Cu 2 Se (JCPDS 24-1131) as secondary phase. The formation of CuInSe 2 films with a chalcopyrite structure and good stoichiometry is observed.Formation of CuInSe2 (CIS) thin films from aqueous solution containing citrate as complexing agent is reported. The surface morphology and the composition of the deposited films are characterized by scanning electron microscopy (SEM). The texture of the deposits and their compositions are analyzed by X-ray diffraction and transmission electron microscopy (TEM). Annealing of the films at 350°C in flowing argon electrodeposited at potentials in the range [-0.24, -0.4 (V vs Ag/AgCl)] resulted in the formation of alpha-Cu 2 Se (JCPDS 24-1131) and CuSe (JCPDS 6-0427). On the contrary, annealing in the same conditions of the films electrodeposited between -0.4 and -0.6 V vs Ag/AgCl led to the formation of chalcopyrite CuInSe 2 (JCPDS 23-209) with alpha-Cu 2 Se (JCPDS 24-1131) as secondary phase. The formation of CuInSe 2 films with a chalcopyrite structure and good stoichiometry is observed
Effect of heat treatment with CdCl2 on the electrodeposited CdTe/CdS heterojunction
CdS/CdTe heterojunction was subjected to chemical treatment commonly used in photovoltaic device fabrication to determine the resulting microscopic effect on the morphology and structure. CdS and CdTe thin films were electrodeposited successively onto indium tin oxide (ITO) from aqueous solution. Containing CdCl2 and Na2S2O3 for the deposition of thin film windows, the ITO/CdS resulting substrates was then used for the deposition of CdTe thin film absorber using aqueous solution of CdSO4 and TeO2. Next CdCl2 dip followed by 400°C heat treatment was used to modify the CdTe/CdS surface and interface. Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) were used to evaluate the resulting surface morphology. X-ray diffraction analysis reveals that the heat treatment enhances the recrystallisation and shifts the CdTe peaks towards a smaller lattice parameter.CdS/CdTe heterojunction was subjected to chemical treatment commonly used in photovoltaic device fabrication to determine the resulting microscopic effect on the morphology and structure. CdS and CdTe thin films were electrodeposited successively onto indium tin oxide (ITO) from aqueous solution. Containing CdCl2 and Na2S2O3 for the deposition of thin film windows, the ITO/CdS resulting substrates was then used for the deposition of CdTe thin film absorber using aqueous solution of CdSO4 and TeO2. Next CdCl2 dip followed by 400°C heat treatment was used to modify the CdTe/CdS surface and interface. Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) were used to evaluate the resulting surface morphology. X-ray diffraction analysis reveals that the heat treatment enhances the recrystallisation and shifts the CdTe peaks towards a smaller lattice parameter
Physical properties of CdSexTe1-x thin films prepared by electrodeposition
The cadmium chalcogenides CdSexTe1-x (0≤x ≤1 ) thin films have been electrodeposited onto ITO coated glass substrates from an acid sulphate solution at 90 °C. The structure, the composition and the morphology have been studied as a function of the x coefficient by XRD, EDAX, optical absorbance and AFM techniques. All deposits have a cubic structure with a preferred orientation along the (111) direction. The composition in the films is found to vary linearly with the composition in the solution. The increase of the amount of tellurium in the CdSexTe1-x films decreases the band gap down to 1.35 eV and increases the lattice constant. The photoelectrochemical studies in a polysulfide electrolyte show that CdSexTe1-x thin films behave as n-type semiconductors.The cadmium chalcogenides CdSexTe1-x (0≤x ≤1 ) thin films have been electrodeposited onto ITO coated glass substrates from an acid sulphate solution at 90 °C. The structure, the composition and the morphology have been studied as a function of the x coefficient by XRD, EDAX, optical absorbance and AFM techniques. All deposits have a cubic structure with a preferred orientation along the (111) direction. The composition in the films is found to vary linearly with the composition in the solution. The increase of the amount of tellurium in the CdSexTe1-x films decreases the band gap down to 1.35 eV and increases the lattice constant. The photoelectrochemical studies in a polysulfide electrolyte show that CdSexTe1-x thin films behave as n-type semiconductors
In situ monitoring of electrophoretic deposition of Cu2ZnSnS4 nanocrystals
Cu2ZnSnS4 (CZTS) nanocrystal (NC) layers were deposited successfully by
electrophoretic deposition (EPD) on molybdenum and fluorine doped tin oxide
coated glass substrates. This approach combines a non-vacuum coating technique
known for its industrial eligibility to a solar absorber material consisting
solely of non-toxic and earth abundant elements. CZTS NC layers with
thicknesses between 200 nm and 1.5 ÎĽm were formed in 0.5 to 1 min while the NC
dispersion, consisting of organic solvents, depleted entirely. Therefore the
layer thickness can be controlled by varying the concentration of NCs in
dispersion. Scanning electron microscopy micrographs show compact and
homogeneous films. The layers were analyzed by grazing incidence X-ray
diffraction, Raman analysis. Optical properties were probed by UV-vis
spectroscopy. The dependence of dispersion composition and applied voltage on
deposition dynamics and duration was analyzed by the use of an optical
monitoring setup. The results open up a route of low cost CZTS thin film
fabrication with reduced chemical contamination, fast layer deposition and
high raw material use
Pyrite nanocrystals: shape-controlled synthesis and tunable optical properties via reversible self-assembly
Nanocrystals from non-toxic, earth abundant materials have recently received great interest for their potential large-scale application in photovoltaics and photocatalysis. Here, we report for the first time on the shape-controlled and scalable synthesis of phase-pure pyrite (FeS2) nanocrystals employing the simple, inexpensive, thermal reaction of iron–oleylamine complexes with sulfur in oleylamine. Either dendritic nanocrystals (nanodendrites) or nanocubes are obtained by adjusting the iron-oleylamine concentration and thereby controlling the nucleus concentration and kinetics of the nanocrystal growth. Pyrite nanodendrites are reversibly assembled by washing with toluene and redispersed by adding the ligand oleylamine. The assembly–redispersion-process is accompanied by an increased absorption in the red/near-infrared spectral region for the aggregated state. This increased low-energy absorption is due to interactions between the closed-packed nanocrystals. High-concentration nanodendrite dispersions are used to prepare pyrite thin films with strong broadband extinction in the visible and near-infrared. These films are attractive candidates for light harvesting in all inorganic solar cells based on earth abundant, non-toxic materials as well as for photocatalytic applications
11.3% efficiency Cu(In,Ga)(S,Se)2 thin film solar cells via drop-on-demand inkjet printing
Although Cu(In,Ga)(S,Se)2 (CIGSe) based thin film solar cells have reached
efficiencies exceeding 22% based on vacuum processed CIGSSe absorbers, the
supply of indium and gallium might become an issue if CIGSSe thin-film solar
cells are produced in very large volumes. It is therefore mandatory to reduce
the wastage of indium and gallium during the fabrication process. In this
work, we report on a highly efficient precursor utilization, and a vacuum-
free, and scalable route to the deposition of Cu(In,Ga)(S,Se)2 (CIGSSe) thin
films via drop-on-demand inkjet-printing. The precursor ink, which shows long-
term stability in air at room temperature, is formulated by dissolving metal
nitrate salts in alcohol-based solvents. Crack free CIGSSe absorbers
consisting of a layer with large grains at the surface and a layer with small
grains at the back have been prepared by annealing the inkjet-printed Cu–In–Ga
nitrate precursors in a Se/H2S containing atmosphere. Ga accumulation has been
observed within the layer with small grains. A solar cell with a total area
efficiency of 11.3% under standard AM 1.5 illumination has been achieved based
on the printed CIGSSe absorbers
Cu2ZnSn(S,Se)4 from CuxSnSy nanoparticle precursors on ZnO nanorod arrays
Solar cells with Cu2ZnSnS4 absorber thin films have a potential for high
energy conversion efficiencies with earth-abundant and non-toxic elements. In
this work the formation of CZTSSe from CuxSnSy nanoparticles (NPs) deposited
on ZnO nanorod (NR) arrays as precursors for zinc is investigated. The NPs are
prepared using a chemical route and are dispersed in toluene. The ZnO NRs are
grown on fluorine doped SnO2 coated glass substrates by electro deposition
method. A series of samples are annealed at different temperatures between 300
°C and 550 °C in selenium containing argon atmosphere. To investigate the
products of the reaction between the precursors the series is analyzed by
means of X-ray diffraction (XRD) and Raman spectroscopy. The morphology is
recorded by scanning electron microscopy (SEM) images of broken cross
sections. The XRD measurements and the SEM images show the disappearing of ZnO
NRs with increasing annealing temperature. Simultaneously the XRD and Raman
measurements show the formation of CZTSSe. The formation of secondary phases
and the optimum conditions for the preparation of CZTSSe is discusse
Synthesis of Cu2ZnxSnySe1+x+2y nanocrystals with wurtzite-derived structure
The most reported stable crystal structure of Cu2ZnSnS4 and Cu2ZnSnSe4 (CZTSe)
is kesterite, which is derived from the ternary chalcopyrite structure.
However, by controlling the reaction conditions, we found that the structure
and composition of the CZTSe nanocrystals (NCs) can be tuned. This can be
achieved by using a simple hot injection approach. The structural properties
of the CZTSe NCs were characterized by powder X-ray diffraction (PXRD), Raman
spectroscopy and transmission electron microscopy. The energy dispersive X-ray
spectroscopy confirms the stoichiometry of CZTSe NCs. The optical band gap of
the NCs is found to be around 1.38 eV, as estimated from UV-Vis absorption
spectroscopy. PXRD studies show that the obtained CZTSe NCs occurring in three
structurally different phases (tetragonal kesterite type, hexagonal wurtzite
type and orthorhombic wurtz-stannite type) are converted to the kesterite
structure by annealing at 540 °C for 30 min under an Se-vapour atmosphere
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