Comparative kinetic studies of the chemical deposition of PbSe with sodium selenosulfate and selenourea with the establishment of the influence of their nature on the composition and morphology of the films

After analyzing the literature, one can note the increased interest in lead selenide in the thin-film state, used in various fields: from microelectronics to solar energy converters. There are physical and chemical methods for producing PbSe films, each of which has its own advantages and disadvantages. However, researchers prefer chemical deposition from aqueous media, which eliminates the need for complex, expensive equipment, heating to high temperatures and creating high pressures. The Ural school of thin-film synthesis has developed and tested a kinetic-thermodynamic method for predicting the chemical deposition of metal chalcogenides. The thermodynamic assessment carried out in our previous publication indicated only the principal possibility of the formation of lead selenide when using selenocarbamide СSe(NH2)2 and sodium selenosulfate Na2SeSO3. For a more complete understanding of this process, a comprehensive approach is necessary, taking into account the patterns of the deposition of the solid phase of PbSe in time, depending on thermodynamic factors - temperature and concentration of reagents. Therefore, in this work, we studied the kinetics of the chemical deposition of lead selenide with selenourea and sodium selenosulfate from solutions containing lead acetate, sodium citrate, ammonium hydroxide and iodide, in the temperature 303 -353 K under conditions of spontaneous nucleation of the solid phase. As a result of the studies, the partial kinetic reaction orders for chalcogenizers were determined, amounting to 0.86 (СSe(NH2)2) and 0.78 (Na2SeSO3), as well as the activation energy of the formation of lead selenide, which amounted to 45.1 and 25.07 kJ/mole, respectively. Hydrochemical deposition of selenocarbamide and sodium selenosulfate produced PbSe films on substrates of sitall and glass with a thickness of 200-300 nm. Energy dispersive analysis and scanning electron microscopy showed the influence of the nature of the substrate, type chalcogenizer on the morphology, particle size distribution and elemental composition of lead selenide layers. An elemental analysis showed that PbSe films precipitated with sodium selenosulfate contain an excess of lead compared to selenium (Pb/Se = 1.25-1.32), and the stoichiometric composition ensures the use of selenocarbamide (Pb/Se = 0.99-1.05).

Chemical bath synthesis of metal chalcogenide films. Part 42. Experimental verification of the deposition regions of PbSe by sodium selenosulfate and selenourea in the presence of various ligands

Calculation of ionic equilibria in the reaction system for synthesis of PbSe thin films was carried out. Three reaction systems containing the following combinations of reagents were considered: sodium citrate with liquid ammonia and sodium selenosulfate (system 1) or selenourea (system 2) used as chalcogenizer, ethilendiamine, sodium acetate and selenourea (system 3).The main lead complex compoundsprevented the fast PbSe formation in system 1 and 2 in region of pH of intensive selenosulfate and selenourea decomposition were hydroxo-citrate complexes. In the system 3 complexes with ethilendiamine and acetate-ions played the most significant role. For evaluating the deposition conditions of the main and impurity phases (metal hydroxides and cyanamides) by thermodynamic calculations taking into account the sizes of critical nucleis, the boundary conditions and regions of formation of PbSe, Pb(OH)2, PbCN2 in the studied reaction systems were found. The calculation results are presented in the form of three-dimensional dependencies in the coordinates “indicator of the initial concentration of the metal salt – pH of the solution – ligand concentration” and “indicator of the initial concentration of the metal salt – pH of the solution – concentration of the chalcogenizer”. Based on the calculations and preliminary experiments, the compositions of the discussed reaction mixtures were formed for the chemical bath deposition of PbSe films, which, in addition to the main components, included a dopant in the form of ammonium iodide. In the synthesis process at a temperature of 353 K (system 1 and 2) for 60 minutes and 308 K for 90 minutes (system 3), using all the studied reaction systems on glass substrates, homogeneous PbSe layers with a thickness of ~500 to ~700 nm were obtained. The ratio between the main elements of Pb and Se in the film varies between 0.98-1.32, and the iodine content is 7-11 at.% depending on the composition of the reaction bath.

AMORPHOUS PbSe THIN FILM PRODUCED BY CHEMICAL BATH DEPOSITION AT pH OF 5–8

Lead selenide (PbSe) thin films have been deposited on amorphous glass substrates at room temperature, using the simple chemical bath deposition technique. Lead sulfate and sodium selenosulfate were used as the source materials to obtain lead selenide films. Transmittance, absorption, optical bandgap and refractive index of the films were investigated via the UV–vis spectrum. Amorphous form was observed in the XRD pattern. The structural and optical properties of PbSe thin films produced at different pH were analyzed. SEM analysis was performed for analyzing the surface of the films. Some properties of the films were observed to vary with pH and these properties were investigated according to the change of pH, for pH values of 5–8. Optical bandgap varied with pH between 1.46[Formula: see text]eV and 1.75[Formula: see text]eV. Film thickness also changed with pH from 465[Formula: see text]nm to 1765[Formula: see text]nm.

Sodium Selenosulfate from Sodium Sulfite and Selenium Powder: An Odorless Selenylating Reagent for Alkyl Halides to Produce Dialkyl Diselenide Catalysts

Na2SeSO3, which can be generated in situ by the reaction of Na2SO3 with Se power, was found to be an odorless reagent for the selenenylation of alkyl halides to produce dialkyl diselenides. These products have been recently shown to be good catalysts for the Baeyer–Villiger oxidation of carbonyl compounds, for the selective oxidation of alkenes, or for the oxidative deoximation of oximes. By using aqueous EtOH as the solvent and avoiding the generation of a malodourous selenol intermediate, the selenylation reaction with Na2SeSO3 is much more environmentally friendly than conventional methods. Owing to the cheap and abundant starting materials and selenium reagents, our novel synthetic method reduces the production costs of dialkyl diselenides as organoselenium catalysts, thereby advancing practical applications of organoselenium-catalysis technologies.

Growth of Bi2Se3 Films by Chemical Bath Deposition at Room Temperature

ABSTRACTBismuth selenide (BixSey) films are deposited onto glass substrate using chemical bath deposition at room temperature. The reacting bath contained bismuth nitrate, triethanolamine and sodium selenosulfate as selenium (Se) source. Ammonium hydroxide is used to adjust the pH of the bath. The films deposited in solutions containing Se source solution of 10 ml and 15 ml are characterized by surface morphological, compositional and structural, properties. The optimum deposition time is about 3 hours for both solutions. Films deposited up to 24 hours in bath with 10 ml Se source solution had thickness ranging up to 232 nm. The deposition rate is found to increase up to 61 nm/h for 3-hour deposition. In the case of bath with 15 ml Se source solution, the film thickness ranged from 45 nm to 632 nm for 1-hour to 24-hour deposition, respectively; with a deposition rate increasing up to 123 nm/h for 3-hour deposition. Film roughness of about 6.6 nm to 22.8 nm is measured by atomic force microscope for films deposited in bath containing 10 mL Se source and 15 ml of Se source, respectively. Crack free layers are observed with randomly large plate-like particles on top of the layer for some films. The films with typical composition of Bi21.8Se78.2 are found to be rich in Se when deposited for 6 hours, whereas the composition of a film deposited in the same bath (10 mL Se source) for 3 hours is found at Bi60.3Se39.6. Additionally, structural analysis performed by x-ray diffraction (XRD) did not reveal well-defined XRD patterns, which indicates that BixSey films were constituted mostly of nanocrystalline grains.

Cu2ZnSnSe4 from Chemically Deposited Binary Films

Chemically deposited thin film stack of SnSe-ZnSe-Cu2-xSe was heated in nitrogen with Se vapor at 350-400 oC to produce Cu2ZnSnSe4 (CZTSe) thin films. For this, a thin film of SnSe with 180 nm thickness was deposited at 26 °C from a chemical bath containing tin(II) chloride, triethanolamine, sodium hydroxide, sodium selenosulfate, and a small quantity of polyvinylpyrrolidone. Thin films of ZnSe and Cu2-xSe were subsequently deposited on this SnSe film, also from chemical bath. The CZTSe thin film produced this way shows X-ray diffraction pattern matching that of Cu2ZnSnSe4 (kesterite/stannite) and have a Zn-rich composition. The film has an optical band gap of 0.9-1.0 eV and p-type electrical conductivity, 0.2-0.06 Ω-1 cm-1.

Chemically Deposited Cd1-xPbxSe Thin Films for Photoelectrochemical Studies

Optimum composition of Cd1xPbxSe thin films (0.1 x 0.9) were deposited using single precursor bath containing cadmium sulfate octahydrate, lead nitrate, tartaric acid, potassium hydroxide, ammonia and sodium selenosulfate onto fluorinedoped tin oxide (FTO) glass substrates. The photoelectrochemical (PEC) cells were fabricated using Cd1xPbxSe as an active photoelectrode with sulphide/polysulphide redox couple as an electrolyte and sensitized graphite rod as a counter electrode. The various characteristics of the cells namely currentvoltage (IV), capacitancevoltage (CV) in dark, power output, builtinpotential, photoresponse, spectral response measurements were investigated. The cell performance parameters such as opencircuit voltage (Voc), shortcircuit current (Isc), series resistance (Rs), shunt resistance (Rsh), conversion efficiency (η), fill factor (FF), junction ideality factor (nd), builtinpotential (ΦB), flatband potential (Vfb) were evaluated. PEC characteristics reveal ntype semiconducting nature for Cd1xPbxSe thin films with lead composition x < 0.5, while ptype nature for remaining Cd1xPbxSe thin films. Among the various cells, the maximum PEC efficiency (η = 1.401 %) was found to Cd0.7Pb0.3Se thin films; due to its increase in opencircuit voltage (225 mV) as well as shortcircuit current (3.983 mA/cm2),decrease in resistance (Rs= 0.75 kΩ and Rsh= 331 Ω), and increase in photoelectrode absorption as compared to other thin film materials.

CdSe Thin Film by Using Spin-Coating

CdSe thin film was prepared by using spin coating method .The surface morphology of CdSe thin films can be used as the main material in solar cells application, by using sodium selenosulfate as a selenium source and cadmium chloride as cadmium precursor. The solution for each sample had with different molar ratio of cadmium chloride and sodium selenosulfate to know the comparison between the samples. The spin for each samples were constant parameter with 3000 rpm at 30 seconds and dry in ambient temperature. The characterization using atomic force microscopy (AFM) to know the surface morphology of CdSe thin film. The important thing in this paper was to know the surface morphology of CdSe thin films as the comparison with other experiment for solar cells application.