Physicochemical features of dielectrical nano-barrier layers in CdSe_xS_1-x films formed by screen printing method

Abstract

The thermal activation process of CdSe x S 1-x films, formed by screen printing, was investigated. We mostly focused on the influence of thermal treatment conditions on oxidised film formation on the crystalline grain surface with nano-barrier "dielectric-semiconductor" layer generation. The composition and thickness of nanobarrier layers were determined by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) methods. The thickness of nano-barrier layers was found to be 2-5 monolayers. It was shown that photoelectric properties of CdSe x S 1-x films were determined by the doping level and nano-barrier layer characteristics. By the use of XRD and SEM methods we experimentally investigated and justified that better microstructure and photoelectric properties (R D / R L ≥ 10 7) of CdSe x S 1-x films are achieved by photosensitivity activation during 15-30 min thermal treatment in quasi-closed air atmosphere at 550 °С or during 5-15 min at 600 °С with low speed cooling (3 °С/min). The manufacturing method for obtaining CdSe x S 1-x films with assigned characteristics determined by paste composition and properties, thermal treatment regime and medium optimisation was developed.

Morphological Features of Polycrystalline CdS1−xSex Films Obtained by Screen-Printing Method

“…The experimental studies [1][2][3] showed that the modes of applying the films onto the polycrystalline glass substrates by screen printing, while choosing a particular web to apply the paste to a substrate, require considering the functional purpose of the applied film. The size of the gap between the stencil and the substrate was selected by varying the sizes of the gap (0.5-4 mm) between the stencil and the substrate during the film deposition.…”

“…The microstructure of CdS 1−x Se x -based films and their most important properties (photoconductivity, luminescence, etc.) depend largely on the type and concentration of precursors, film production technology, and thermal activation of photoconductivity [1][2][3][4]. During thermal activation, the crystallites of films are oxidized, as a result of which, an oxide phase-semiconductor barrier is formed on their surface, the parameters of which can be controlled by optimizing the processing temperature range and the gas medium composition, as well as the composition of the applied pastes.…”

“…Additionally, the patterns of change in composition and microstructure properties can provide valuable information on the behavior of impurities and defects originating in the materials. Semiconductor materials can be obtained the most easily and cheaply in the form of polycrystalline films, so clarifying the above patterns for polycrystalline films is an urgent task [2,3].…”

“…Polycrystalline films based on CdS 1−x Se x (0 ≤ x ≤ 1) under certain conditions of preparation have high photoconductivity at room and close to room temperatures and, thus, attract the attention of material engineers and manufacturers of new devices, in particular, manufacturers of solar panels and photoresistors [3,4].…”

“…In the scientific literature, glass, or ceramic or polycrystalline glasses, are known to be the most often used as substrates. According to the combination of dielectric and mechanical properties, surface microrelief, and chemical resistance, the most acceptable material for screen-printing substrates is polycrystalline glass [2,3].…”