A. Mere

Composition and structure of CuInS2 films prepared by spray pyrolysis

Abstract CuInS2 thin films have been prepared by spray pyrolysis of an aqueous solution of CuCl2, InCl3 and thiourea onto heated glass substrates. The effect of the composition of starting solutions on the phase and chemical composition and the structure of sprayed films is studied. The Cu/In ratio in the films is higher than that in the solution. In-rich and S-rich solutions lead to the multiphase films with poor crystallinity according to X-ray diffraction. It was determined that organic phases as products of the thermal decomposition of thiourea ligand are present in the films at all used solution compositions. The formed organic secondary phases could be responsible for the formation of molten phase which together with copper sulphide act as recrystallisation agent during the growth of copper-rich films. The CuInS2 films, strongly orientated in the (112) direction with crystallites up to 300 nm in the matrix and with large crystals of some microns in agglomerated areas, are formed while the secondary phases segregated on the thin film surface.

Composition of CuInS2 thin films prepared by spray pyrolysis

CuInS 2 films were prepared by spray pyrolysis technique using CuCl 2 , InCl 3 and SC(NH 2 ) 2 as initial chemicals. The content of Cl, O, C and N impurities in sprayed CuInS 2 films were measured by EDS, WDS, RBS and organic elemental analysis. The growth temperatures of 260-280°C result in Cl, C, N content of 8 mass% and the impurity phases contain SCN, CN, NH, SO 4 groups as identified by FTIR. The increase in the growth temperature up to 380°C decreases the concentration of Cl, C, N to 1-2 mass%, concurrently leading to oxidation of inorganic and organic phases resulting in O content of 16.7 at.%. The content of impurities originated from precursors is mainly controlled by the growth temperature and in less extent by the Cu/In ratio in spray solution as Cu-rich solutions result in the films with reduced content of organic residues. Thermal treatments in reducing atmospheres at 450°C improves the crystallinity of the films while annealing in flowing H 2 effectively reduces the content of Cl and O impurities.

Photoluminescence of spray pyrolysis deposited ZnO nanorods

Photoluminescence of highly structured ZnO layers comprising well-shaped hexagonal rods is presented. The ZnO rods (length 500-1,000 nm, diameter 100-300 nm) were grown in air onto a preheated soda-lime glass (SGL) or ITO/SGL substrate by low-cost chemical spray pyrolysis method using zinc chloride precursor solutions and growth temperatures in the range of 450-550°C. We report the effect of the variation in deposition parameters (substrate type, growth temperature, spray rate, solvent type) on the photoluminescence properties of the spray-deposited ZnO nanorods. A dominant near band edge (NBE) emission is observed at 300 K and at 10 K. High-resolution photoluminescence measurements at 10 K reveal fine structure of the NBE band with the dominant peaks related to the bound exciton transitions. It is found that all studied technological parameters affect the excitonic photoluminescence in ZnO nanorods.PACS: 78.55.Et, 81.15.Rs, 61.46.Km

ZnO Nanorods via Spray Deposition of Solutions Containing Zinc Chloride and Thiocarbamide

In this work we present the results on formation of ZnO nanorods prepared by spray of aqueous solutions containing ZnCl2and thiocarbamide (tu) at different molar ratios. It has been observed that addition of thiocarbamide into the spray solution has great impact on the size, shape and phase composition of the ZnO crystals. Obtained layers were characterized by scanning electron microscopy (SEM) equipped with energy selected backscattered electron detection system (ESB), X-ray diffraction (XRD) and photoluminescence spectroscopy (PL). Small addition of thiocarbamide into ZnCl2solution (ZnCl2:tu = 1:0.25) supports development of significantly thinner ZnO nanorods with higher aspect ratio compared to those obtained from ZnCl2solution. Diameter of ZnO rods decreases from 270 to 100 nm and aspect ratio increases from ∼2.5 to 12 spraying ZnCl2and ZnCl2:tu solutions, respectively. According to XRD, well crystallized (002) orientated pure wurtzite ZnO crystals have been formed. However, tiny ‘spot’—like formations of ZnS were detected on the side planes of hexagonal rods prepared from the thiocarbamide containing solutions. Being adsorbed on the side facets of the crystals ZnS inhibits width growth and promotes longitudinalc-axis growth.

CuInS2 sprayed films on different metal oxide underlayers

Abstract CuInS 2 films as absorbers for solar cells were deposited by the spray pyrolysis method onto commercial ITO and TCO glasses and two different types of TiO 2 and ZnO electrodes—flat and porous. Structural, morphological and electrical properties of metal oxide/CuInS 2 structures have been studied. CuInS 2 crystallite sizes of 6–10 nm on flat electrodes and of 20–30 nm on randomly orientated porous underlayers have been calculated. Doped large band gap oxides are found to be appropriate conductive electrodes for CuInS 2 deposited with the spray process. Flat TiO 2 /CuInS 2 and ZnO:In/ZnO/CdS/CuInS 2 solar cell structures, entirely prepared by spray technique, show output characteristics of U OC =373 mV, j SC =3.5 mA/cm 2 and U OC =430 mV, j SC =8.1 mA/cm 2 , respectively. The penetration of CuInS 2 into microporous and columnar structures has been confirmed by scanning electron microscopy studies.

Magnetic and structural studies of LaMnO3 thin films prepared by atomic layer deposition

Here we report the results of structural, microstructural and magnetic property characterizations of both thin films and bulk samples of LaMnO3 (LMO). Thin films were deposited by the atomic layer deposition technique on silicon (1 0 0) substrates, whereas bulk samples were prepared by a citrate combustion route. Effects of varying thickness, annealing atmosphere and temperature were studied on both LMO sample classes. Single-phase perovskite crystal structure was confirmed by x-ray diffraction and Raman spectroscopy, in thin films annealed at 700 and 800 °C as well as in bulk samples. Thin films annealed in N2 or O2 atmosphere do not vary in the crystal structure, but differ by the oxygen stoichiometry, microstructure and magnetic properties. The Curie temperature in all LMO thin films annealed in N2 was found to be around 200 K, while it was around 250 K for the films annealed in O2 as well as for the bulk samples.

Effect of solution spray rate on the properties of chemically sprayed ZnO: in thin films

ZnO:In thin filmswere grown from 100 mL of spray solution on glass substrates by chemical spray at Ts = 400°Cusing solution spray rates of 0.5-6.7 mL/min. Zinc acetate and indium(III)chloride were used as Zn and In sources, respectively, with [In]/[Zn] = 3 at.%. Independent of solution spray rate, the crystallites in ZnO:In films grow preferentially in the (101) plane parallel to the substrate. The solution spray rate influences the surface morphology, grain size, film thickness, and electrical and optical properties. According to SEM and AFM studies, sharp-edged pyramidal grains and canvas-resembling surfaces are characteristic of films grown at spray rates of 0.5 and 3.3 mL/min, respectively. To obtain films with comparable film thickness and grain size, more spray solution should be used at low spray rates. The electrical resistivity of sprayed ZnO:In films is controlled by the solution spray rate. The carrier concentration increases from 2ċ1019 cm-3 to 1ċ1020 cm-3 when spray rate is increased from0.5 mL/min to 3.3 mL/min independent of the film thickness; the carrier mobilities are always lower in slowly grown films. Sprayed ZnO:In films transmit 75-80% of the visible light while the increase in solution spray rate from0.5 mL/min to 3.3 mL/min decreases the transmittance in the NIR region and increases the band gap in accordance with the increase in carrier concentration. Lower carrier concentration in slowly sprayed films is likely due to the indium oxidation.

Sb2S3 grown by ultrasonic spray pyrolysis and its application in a hybrid solar cell

Chemical spray pyrolysis (CSP) is a fast wet-chemical deposition method in which an aerosol is guided by carrier gas onto a hot substrate where the decomposition of the precursor chemicals occurs. The aerosol is produced using an ultrasonic oscillator in a bath of precursor solution and guided by compressed air. The use of the ultrasonic CSP resulted in the growth of homogeneous and well-adhered layers that consist of submicron crystals of single-phase Sb2S3 with a bandgap of 1.6 eV if an abundance of sulfur source is present in the precursor solution (SbCl3/SC(NH2)2 = 1:6) sprayed onto the substrate at 250 °C in air. Solar cells with glass-ITO-TiO2-Sb2S3-P3HT-Au structure and an active area of 1 cm2 had an open circuit voltage of 630 mV, short circuit current density of 5 mA/cm2, a fill factor of 42% and a conversion efficiency of 1.3%. Conversion efficiencies up to 1.9% were obtained from solar cells with smaller areas.

Low-cost plasmonic solar cells prepared by chemical spray pyrolysis

Summary Solar cells consisting of an extremely thin In2S3/CuInS2 buffer/absorber layer uniformly covering planar ZnO were prepared entirely by chemical spray pyrolysis. Au nanoparticles (Au-NPs) were formed via thermal decomposition of a gold(III) chloride trihydrate (HAuCl4·3H2O) precursor by spraying 2 mmol/L of the aqueous precursor solution onto a substrate held at 260 °C. Current–voltage scans and external quantum efficiency spectra were used to evaluate the solar cell performance. This work investigates the effect of the location of the Au-NP layer deposition (front side vs rear side) in the solar cell and the effect of varying the volume (2.5–10 mL) of the sprayed Au precursor solution. A 63% increase (from 4.6 to 7.5 mA/cm2) of the short-circuit current density was observed when 2.5 mL of the precursor solution was deposited onto the rear side of the solar cell.

Room-temperature ferromagnetism in Ca and Mg stabilized cubic zirconia bulk samples and thin films prepared by pulsed laser deposition

We report room-temperature ferromagnetism in Ca and Mg stabilized zirconia bulk samples and thin films. Powders were prepared by the citrate-combustion route, and thin films grown on silicon substrates by the pulsed laser deposition technique. X-ray diffractograms and Raman spectra at room temperature reveal the formation of cubic phase zirconia. The observed ferromagnetism is robust at room temperature in both bulk as well as in thin film samples, although it is weaker in thin films. The origin of the ferromagnetism can be related to oxygen vacancies created due to divalent (calcium and magnesium) substitution for tetravalent zirconium ions. (Some figures may appear in colour only in the online journal)