Chemical Surface Deposition Research Articles

Mathematical approaches to a method of semiconductor materials films synthesis type AiiBvi for photosensitive structures used in alternative energy

The scientific direction of the synthesis of CdS and CdSe thin films by the method of chemical surface deposition (CSD) using aqueous solutions of cadmium-containing salts: chloride, nitrate, sulfate, acetate, iodide has been developed. A mathematical model of the CSD process of CdS and CdSe thin films was developed to improve the efficiency of experiments and reduce costs. The model makes it possible to determine the concentration of reagents, the duration, and the CSD temperature, which are necessary to obtain films of a specified thickness. The optimization of chemical deposition parameters of film-type semiconductor materials has been carried out. Based on the mathematical model, the optimal synthesis conditions were the next: concentration of cadmium-source salt - 0.01 mol/L, chalcogenizer - 1.0 mol/L or 0.1 mol/L in the chase of thiourea or sodium selenosulfate, respectively; temperature - 70?C and duration of 3 min. The mathematical dependence of the experimental studies results of the metal ions content in thin-film solar cells for the effective direct conversion of solar radiation into electrical energy taking into account errors was proposed.

A Comparative Study of (Cd,Zn)S Buffer Layers for Cu(In,Ga)Se2 Solar Panels Fabricated by Chemical Bath and Surface Deposition Methods.

Scale-up to large-area Cu(In,Ga)Se2 (CIGS) solar panels is proving to be much more complicated than expected. Particularly, the non-vacuum wet-chemical buffer layer formation step has remained a challenge and has acted as a bottleneck in industrial implementations for mass-production. This technical note deals with the comparative analysis of the impact on different methodologies for the buffer layer formation on CIGS solar panels. Cd(1-x)ZnxS ((Cd,Zn)S) thin films were prepared by chemical bath deposition (CBD), and chemical surface deposition (CSD) for 24-inch (37 cm × 47 cm) patterned CIGS solar panel applications. Buffer layers deposited by the CBD method showed a higher Zn addition level and transmittance than those prepared by the CSD technique due to the predominant cluster-by-cluster growth mechanism, and this induced a difference in the solar cell performance, consequently. The CIGS panels with (Cd,Zn)S buffer layer formed by the CBD method showed a 0.5% point higher conversion efficiency than that of panels with a conventional CdS buffer layer, owing to the increased current density and open-circuit voltage. The samples with the CSD (Cd,Zn)S buffer layer also increased the conversion efficiency with 0.3% point than conventional panels, but mainly due to the increased fill factor.

In Ukrainian

The purpose of this work is to develop a technology for the production of CdS films by chemical surface deposition on porous substrates of nanocrystalline silicon. The possibility of using the heterostructure CdS/porous-Si/p-Si as photovoltaic solar energy converters is considered. The formation of layers CdS was carried out by the method of precipitation in a chemical bath from an aqueous solution. As a template, plates of porous silicon (Si) are used. Nanoporous silicon was obtained by electrochemical etching of single-crystal plates Si (100) of p-type conductivity with a specific impedance of 6 mΩ•cm. For the chemical surface deposition of CdS films, a freshly prepared 0.015 M aqueous solution of cadmium chloride CdCl 2 , 1.5 M solution of thiourea CH 4 N 2 S, and 14.28 M solution of ammonium hydroxide NH 4 OH were used. The process of heating the plates lasted 5 min. The final temperature was 80 °C. The morphology of the porous silicon surface, the cross-section of the resulting CdS/porous-Si/p-Si structures and the chemical composition of the films obtained were investigated using a scanning electron microscope. The chemical composition of the film surface was determined using X-ray spectral microanalysis. According to the results of the conducted studies, it has been found that the thickness of the CdS layer is homogeneous and is 10–30 microns. CdS films have n-type conductivity. X-ray diffractograms of the sample exhibit pronounced peaks at 2θ ≈ 26.5° and at 2θ ≈ 43.3°, which correspond to the hexagonal modification of CdS. There are also intense peaks from the silicon substrate. A solar photocell is produced, which is a heterostructure of n-CdS/porous-Si/p-Si. The value of the efficiency of the received solar cells exceeds 5.4 % of the efficiency value for similar structures of CdS/p-Si under the same conditions for obtaining a conductive film of n-type CdS. Thus, the heterostructures CdS/porous-Si/p-Si produced by the precipitation of CdS layers in a chemical bath from an aqueous solution can be used as the basis of photovoltaic converters for solar energy.

Development of Cu(In,Ga)Se2 superstrate devices with alternative buffer layers

Superstrate Cu(In,Ga)Se2 (CIGS) solar cells are prepared in the structure SLG/TCO/buffer/CIGS/Au with CIGS deposited onto the buffer layer by a single stage co-evaporation process. Three buffer materials – CdS deposited by chemical surface deposition, ZnSe and ZnO by RF magnetron sputtering – are tested in the superstrate structure. The best cell achieves 8.6% efficiency with the ZnO buffer after light soaking and forward bias treatments. The efficiency of devices with CdS or ZnSe buffers are less than 4%. The junction formation between the absorber and buffer layers are investigated by x-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. For CdS/CIGS and ZnSe/CIGS superstrate devices extensive inter-diffusion between the absorber and buffer layer under CIGS growth condition is the critical problem. For ZnO/CIGS superstrate cells GaxOy formation at the junction interface and unfavorable conduction band alignment are the main factors that limit the device performance.

Modeling of Chemical Surface Deposition (CSD) of CdS and CdSe Semiconductor Thin Films

A mathematical model of the chemical surface deposition process of CdS and CdSe thin films, which allows determining the concentration of reagents, as well as duration and temperature for CSD needed to obtain films of the set thickness was designed. The adequacy of model was tested by Fisher's criterion. The nomogram of dependence of cadmium ions content on the initial deposition parameters was built according to the results of experimental studies and approximated by mathematical dependence.

Growth of thin CdS films on glass substrates via reaction of thiourea with cadmium acetate in aqueous solution

Thin CdS films have been produced by chemical surface deposition from aqueous solutions of cadmium acetate, Cd(CH3COO)2. We have studied the morphology and optical properties of the CdS films and calculated the mechanical stress induced by the difference in linear thermal expansion coefficient between the film and substrate materials.

Chemical surface deposition and growth rate of thin CdSe films

Chemical surface deposition of thin CdSe films was studied. The conditions for preparing thin films were examined, the degrees of Cd conversion in the starting compounds were determined, and the film thicknesses were measured.

Chemical surface deposition of Cd(S,Se) films: influence of the starting cadmium-containing salt on microstructure and optical properties

Chemical surface deposition of Cd(S,Se) films: influence of the starting cadmium-containing salt on microstructure and optical properties

Direct on chip cadmium sulfide thin film transistors synthesized via modified chemical surface deposition

A simple and inexpensive solution-based method to grow functional and continuous nano-crystalline CdS thin films is demonstrated. The resulting CdS films are used to fabricate n-type thin film transistors (TFTs) with field effect mobility as high as ∼0.55 cm2 V−1 s−1, a threshold voltage (VT) of ∼8.4 V, and an on/off current ratio of 106. This method utilizes a solid-state reaction at low temperature that eliminates the need for nanoparticle synthesis to fabricate the semiconducting layer in the TFTs. The method also promotes efficient usage of the chemical precursors, which further reduces the cost of the process. This is a promising method that could be easily implemented in a manufacturable process such as roll-to-roll.

Photosensitivity of n-CdS/p-CdTe heterojunctions obtained by chemical surface deposition of CdS

A new technology of chemical surface deposition is developed, and thin CdS films (35–100 nm) on the p-CdTe substrates are obtained. Electrical and photoelectric properties of n-CdS/p-CdTe heterojunctions are studied, and it is shown that the developed method provides high efficiency of photoconversion in the range restricted by the CdTe and CdS band gaps. It is shown that the method of chemical surface deposition of CdS can be used in the design of thin-film n-CdS/p-CdTe.

Cds thin films fabricated by layered chemical surface deposition from CdCl2 aqueus solution

Cds thin films fabricated by layered chemical surface deposition from CdCl2 aqueus solution

Coking of a Porous Catalyst and Its Inhibiting by Siliconiting Modification

In order to inhibit the coke deposition on the surface of ZSM-5, used as the catalyst for oxidation of benzene to phenol (BTOP) by nitrous oxide, the method of chemical surface deposition of silicon is chosen to modify the surface of ZSM-5. In this paper, the effect of modification condition on the micropore structure and catalyst activity was studied. The porous catalyst was characterized by XRF, EPMA, TEM, XRD, N2 adsorption at −196° C, and pyridine adsorption-infrared techniques. The results show that the uniform SiO2 membrane can be formed on an external surface of the ZSM-5 crystal under moderate modification conditions. The SiO2 membrane covers the acid centers on ZSM-5 external surface, so ZSM-5 external surface coking is inhibited and the pore blockage is avoided or decreased. At the same time, the SiO2 membrane does not change the acid centers located in pores so that the catalyst activity and stability can be improved efficiently. The optimal siliconiting conditions were determined by experiments. Compared with the samples without siliconiting treatment, the samples treated under the optimal conditions can increase the productivity of phenol by 14% for 3 h reaction time and by 41% for 6 h reaction time, respectively.

A STUDY ON ACIDITY AND CATALYTIC PROPERTY OF [B] ZSM-5 CATALYST MODIFIED WITH SILICON COMPOUND BY CHEMICAL SURFACE DEPOSITION OF LIQUID-PHASE TECHNIQUE

ABSTRACT The boron heteroatom zeolite catalyst has been modified with silicon compound by Chemical Surface Deposition of Liquid-phase (CLD) technique and the catalytic property of the modified catalyst is studied. Meanwhile, the acidity of the modified zeolite catalysts is characterized through TPD and IR technique, and the fluid adsorption method is used to determine its pore structure. The relationship between the catalytic property of the zeolite catalyst and its pore structure, its acidity has been found. The results of toluene–ethylene alkylation reaction indicate that the selectivity of p-ethyltoluene on the modified zeolite catalyst is higher than that on the zeolite catalyst before silanizated, reaching 94.14%.