Abstract
Films based on nickel (II) oxides and hydroxides are used in electrochromic cells as one of the active materials that change their optical characteristics under the action of an electric current. Electrochemical deposition, due to which composite films of Ni(OH)2-polyvinyl alcohol (PVA) can be formed on the electrically conductive substrate, can become an alternative to expensive vacuum methods. The presented study is devoted to the study and improvement of the electrochemical method of deposition of Ni(OH)2-PVA electrochromic composite films.This study illustrates the influence of the grade of the used polyvinyl alcohol on the main qualitative characteristics of Ni(OH)2-PVA electrochromic composites. Four PVA grades have been used for the study: 17–99, 24–99, 30–99, and 30–88, which differ in the viscosity of solutions and the degree of hydrolysis. The deposition has been carried out by the electrochemical method in the presence of the listed grades of polymers dissolved in the electrolyte.As a result of the study, it has been shown that the properties of electrochromic films depend on the grade of PVA used. To a greater extent they depend on the degree of hydrolysis, and to a lesser extent – on the molecular weight of the polymer, expressed in terms of viscosity.Analysis of the data obtained makes it possible to assert that the degree of PVA hydrolysis has a greater effect on the final characteristics of the films than the viscosity of solutions. However, viscosity also affects the properties. Moreover, it has been found that there is some optimum for this value. In this case, in terms of the characteristics of the films obtained, the optimal PVA has been the one with an average viscosity (PVA 24-99) among polyvinyl alcohols of three grades with the same degree of hydrolysis. The results obtained make it possible to recommend the use of PVA with an average viscosity and a degree of hydrolysis of less than 99 %. Based on the literature data, assumptions have been made that allow explaining the results obtained by the change in the hydrophobicity of the film and the properties of the transparent SnO2:F layer on glass.
Highlights
Electrochromism is a phenomenon associated with a change in the optical properties of systems when an electric current is passed through them [1, 2]
The study aimed to determine the effect of different polyvinyl alcohol (PVA) grades on the properties of electrochromic composite films of Ni(OH)2-PVA when deposited on glass coated with an electrically conductive transparent oxide
Specific characteristics of Ni(OH)2-PVA films deposited by the cathodic template method in the presence of different PVA grades on conductive glass substrates coated with SnO2:F have been determined
Summary
Electrochromism is a phenomenon associated with a change in the optical properties of systems when an electric current is passed through them [1, 2]. Devices based on systems exhibiting electrochromism can be used in various fields – in the advertising industry, in the creation of multimedia devices, in the aviation, auto, and construction industries In this case, electrochromic elements are mainly positioned as working elements of various displays and so-called “smart” windows. Nickel (II) hydroxide is one of the promising materials that can be used in electrochromic devices [13] This material belongs to those, in which a change in the optical state is achieved by an electrochemical reaction with the formation of NiOOH from Ni(OH). This material belongs to those, in which a change in the optical state is achieved by an electrochemical reaction with the formation of NiOOH from Ni(OH)2 It was shown in [14] that a composite material based on Ni(OH) and polyvinyl alcohol (PVA) had advantages over pure Ni(OH). The study and development of alternative methods of applying electrochromic coatings is an urgent task on the way to reduce the cost and, the widespread introduction of electrochromic devices
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