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SnO2 substrate effects on the morphology and composition of chemical bath deposited ZnSe thin films

ZnSe thin films are deposited by the chemical bath deposition (CBD) method onto different glass and SnO2 coated glass substrates. Three SnO2 substrates with different grain size, roughness, conductivity and optical transmission are used. The roughness of the surfaces increases after CBD deposition of ca 0. l μm thick ZnSe films and further upon heating at 200°C due to recrystallisation of the deposit. This effect seems more intense the bigger the grain size of the SnO2 substrate. Above 400°C annealing temperature, the roughness of the films diminishes below that of bare SnO2 substrates, after conversion of ZnSe into a ZnO film. For films deposited on glass substrates, the annealing process gives rise to the roughest surfaces, due to a weaker film-substrate interaction and more important recrystallisation. The optical characterisation shows a decrease in the integral transmittance by about 15% for all the substrates studied after deposition of the ZnSe film. On the glass substrate, the annealing treatment shifts the absorption edge to longer wavelengths reflecting the important recrystallisation. This effect does not take place with SnO2 substrate due to the better crystallinity of the initial film and the stronger film-substrate interaction. Transmittance increases after annealing at 400°C due to the formation of the ZnO film. Compositional analysis by XPS shows that films are composed of a mixture of ZnSe and ZnO, the proportion differing among substrates. In general, films deposited on SnO2 have higher proportion of ZnO than on glass substrate. We attribute this effect to differences in the chemical deposition process induced by the substrate surface.

Photovoltaic windows by chemical bath deposition

Abstract The paper presents a scope of different studies performed on thin-film materials, commonly used as window layers in polycrystalline thin-film solar cells, and prepared by the chemical bath deposition (CBD) method. The presented studies try to offer an approach to some key points of the chemical preparation that are directly related to the final quality and properties of the films. Results on cadmium sulphide (CdS), cadmium sulphide-transparent conductive oxides interfaces (CdS/TCO (ZnO and ITO)), zinc selenide (ZnSe) and indium hydroxy-sulphide In(OH) x S y , are presented and discussed.

Chemical bath deposition of indium hydroxy sulphide thin films: process and XPS characterization

Indium hydroxy sulphide thin films have been deposited from an acidic bath using indium (III) chloride, thioacetamide and acetic acid as complexing agent. It has been found that the proper control of deposition conditions significantly influences the film quality and reproducibility as well as the film thickness. XPS measurements have been carried out for samples prepared using different reactant concentrations in order to study variations in the surface composition. Some films have been also air-annealed at 300 and 400°C to know in which way the composition is affected by this processing. Films are formed by indium hydroxy sulphide, indium oxide and indium sulphate having contaminant species adsorbed on the surface. All samples annealed have shown an oxygen incorporation from the air and an important sulphur loss. The S/In atomic ratio in the indium hydroxy sulphide compound is about one for the non-annealed samples showing that the compound is sulphur deficient. When samples are annealed at 400°C, this value is decreased down to 0.3 owing to the formation of sulphur containing volatile species. The molecular formula for the indium hydroxy sulphide as deposited can be close to InOHS with slight variation in the OH:S proportion depending on the deposition conditions and the annealing temperature.

Reaction mechanism and kinetics for the chemical bath deposition of In(OH)xSy thin films

The solution chemistry of InCl 3 -CH 3 CSNH 2 -CH 3 COOH (InCl 3 -TA-HAcO) system has been studied and the species distribution diagrams, solubility and precipitation curves have been calculated. At an acidic pH (1-4), the (InCl 3 -TA-HAcO) solution contains mainly indium-chloro-complexes and In(OH) 3 precipitation is not expected when HAcO is added. Kinetic calculations based on TA hydrolysis have shown that indium hydroxide-sulfide [In(OH) x S y ] precipitation takes place through a mechanism faster than TA hydrolysis, probably a direct reaction between TA and any indium-chloro-complex, leading to different products depending on the pH of the deposition solution.

Effect of Additives on the Durability and Properties of Antireflective Films for Solar Glass Covers

Generally, single layer antireflective (AR) coatings are based on SiO 2 for which the low refractive index is achieved by increasing the porosity of the films. On the other hand, the increase of porosity on any material results in a decrease of its mechanical properties. In addition to increasing the solar transmittance, it is equally important that the AR film is long-term stable for its application in solar collectors. In this sense, the objective of our work has been to develop a film that exhibits good AR properties and physical durability as well. In the present study, sol-gel silica films have been deposited on borosilicate glass. The effect of adding some organic compounds to the precursor solution in the properties of the films has been studied. Moreover, accelerated weathering tests have been performed in order to investigate the outdoor durability. A value of solar transmittance as high as 0.974 has been obtained by using a porosity promoter additive. However, the durability tests have shown the necessity of incorporating a hydrophobic additive to the precursor solutions in order to avoid the degradation of the optical properties of the films. 1.5% decrease in solar transmittance is observed after 1900 h in the weathering chamber for films prepared with methyltriethoxysilane.

Study of CIGS/In(OH)xSy heterojunctions

Abstract In(OH) x S y buffer layers have been deposited on glass/Mo/CIGS substrates. Composition, reflectance and morphology of those heterojunctions have been studied. The XPS results have shown that the CIGS substrate does not influence the buffer layer composition, which only depends on deposition conditions. Nevertheless, strong variations of CIGS total reflectance take place after the deposition of this buffer layer. It has been also observed that the In(OH) x S y layer shapes the CIGS substrate and totally covers its surface.

Study of thermocline development inside a dual-media storage tank at the beginning of dynamic processes

This work presents some of the experimental results obtained during a test campaign performed at the STONE facility of CEA-Grenoble in collaboration with CIEMAT-PSA supported by both the SFERA-II and the STAGE-STE project. This installation consists of a thermocline tank with thermal oil and rock/sand filler and the tests aimed to study the development of the temperature profile inside the tank at the beginning of charge/discharge processes. The investigation of how this profile is created and which is its dependence on the experimental parameters is crucial for predicting the behavior of a dual-media thermocline tank. Tests have been performed for dynamic processes from initial states with constant uniform temperature or with a thermal gradient already present due to a partial thermocline zone extraction in the former process. Tests at different fluid velocities and temperatures have been carried out as well, in order to evaluate the influence of operating conditions. When a dynamic process of charge or ...

CBD-In(OH) x S y Thin Films: An Approach to the Growth Mechanism

The surface morphology of chemical bath deposited In(OH) x S y thin films has been studied using SEM and TEM. Different surface morphologies have been obtained depending on the deposition conditions (reactant concentrations, pH and bath temperature) as a consequence of the variation of both the homogeneous nucleation and particle-growth rates with them. The In(OH) 3 colloids present in the bulk solution and on the substrate surface play an important role in the growth mechanism since they promote the In(OH) x S y formation. It has been found that the growth mechanism of the films is the socalled particle-by-particle or colloidal growth.

Alloying and selenization of Cu-In stacked layers evaporated onto large areas

In this work, Cu and In thin films, as precursors for CuInSe 2 (CIS) formation, have been deposited on glass substrate up to 30 × 30 cm 2 area using an electron beam evaporator in sequential processes. In order to obtain a similar global composition, three types of sequential processes of evaporation: A) Cu/In/Cu/In, B) Cu/In/Cu/In/Cu/In and C) In/Cu/In/Cu have been tested. As-grown thin films were studied at room temperature and after 120° C annealing. XRD analysis of these films showed mainly the CuIn 2−x (0≤ × ≤ 1) phase at room temperature, and Cu 11 In 9 after annealing at 120° C. After alloying, the films were selenized at temperature between 250° and 400° C in vacuum using elemental selenium vapour. XRD of the selenized thin films corresponding to In/Cu/In/Cu sequence and previously annealing at 120° C, showed the major presence of the polycrystalline chalcopyrite structure CuInSe 2 with preferential orientation (112) plane at temperature as low as 250° C. From SEM studies and profilometer measurements a decrease in the mean roughness could be observed after annealing at 120° C. In contrast the resistivity of the films increased.