Structural, morphological and optoelectronic properties of screen-printed film deposited using Sb2Se3 nanowires

Abstract

Structural, morphological and Optoelectronic properties of Sb2Se3 film prepared by optimized screen-printing method is investigated and presented in this work. Sb2Se3 nanowires synthesized by microwave assisted solvothermal method along with ethylene glycol is used as the ink for the preparation of Sb2Se3screen printed film. Structural analysis confirms the orthorhombic phase while the energy dispersive spectroscopy confirms the formation of Sb2Se3 composition. Crystallite size of the nanocrystalline powder (film) is found to be 60nm (104nm). The surface morphological properties as investigated from field emission scanning electron microscope (FESEM) show that the film is covered with nanowires of length 1-3μm and diameter 100-200nm uniformly distributed over the substrate but agglomerated uniformly as a spherical particle with diameter of ~0.8μm.Interestingly, optoelectronic properties of the film and nanocrystalline powder show a band gap value of 1.19eV and 1.22eV respectively with an infinitesimal change in the band gap of the order of 0.03eV which is in correspondence with the morphological properties.Sb2Se3 being a potential material for solar cells, photodetectors and thermoelectric applications, this combination of fast and facile solvent-mediated microwave synthesis and screen-printing approach exhibits importance towards the wearable technology application for harvesting alternate electrical energy. INTRODUCTION V-VI group binary compounds are typical narrow band semiconductors and their nanostructures are of prime interest because of their dimensional-dependent properties [1]. Among these materials, antimony selenide (Sb2Se3) has gained great attention because of its potential technical applications in many areas including photoelectric, photoluminescence, thermoelectric and photon conducting devices. [1] Research on nanotechnology concerns the fabrication of nanomaterials and their applications in a variety of areas. From last few decades it has emerged as a fast-growing field as the properties of nanomaterials are quite different than to those of bulk materials. In particular, one dimensional nanostructure such as nanowires, nanorods and nanotubes have attracted considerable attention due to their potential use in optical, electronic, magnetic and mechanical devices [2]. Among these compounds, the direct band-gap semiconductor Sb2Se3 (Eg ≈ 1.11 to 1.8 eV), with an orthorhombic crystal structure and Pbnm space group, has been extensively studied as an important thermoelectric material and photoconductive semiconductor and because of its high thermoelectric power (~1800μV/K) and unique solar characteristics [3.] It can be used in thermoelectric applications, as absorber in solar cells memory switching devices, [4,5]. In the past decade, various chemical methods have been developed for the synthesis of Sb2Se3 and other chalcogenide nanomaterials, such as vapor-phase processing, the template-directed method, the solgel route, the microwave-assisted chemical bath method, and hydrothermal/solvothermal synthesis. All of these methods have advantages and disadvantage [3.] Therefore, developing a rapid, green, high-yield synthesis of uniform Sb2Se3nanowires is still highly desired. Here we successfully synthesized Sb2Se3 nanostructures via a reliable and facile method. However, as far as we know, most of previous studies involve high-toxic reducing agent, timeconsuming protocol and exhibit low yield feature. Further, Sb2Se3 thin film can be deposited by different of deposition techniques, such as chemical bath deposition (CBD), vapor transport deposition (VTD), co-evaporation and so on. All these techniques are high cost and involves a lengthy procedure for the preparation of the film, so a low cost and less time-consuming technique is desirable. Screen printing is as such a low cost and fast results giving techniques [6]. Wet deposition of nanocrystalline -based colloidal inks using screen printing, inkjet printing, direct writing, or other layer-by-layer methods hold many advantages due to the ability to directly convert nanocrystalline inks into micro/macroscale functional materials and devices with great scalability, flexibility, and cost effectiveness Now a days, screen printing has also been explored as a more efficient way to fabricate thermoelectric devices [7]. We have prepared the film in air atmosphere by screen printing method and investigated its optoelectronic and structural properties. Surface morphology of the nanocrystalline powder Sb2Se3 and screen printed Sb2Se3film has also been investigated and reported in this work. EXPERIMENTAL DETAILS Sb2Se3 nanostructures has been synthesized via fast and facile microwave assisted solvothermal process. Sb2Se3 has been synthesized in the nanocrystalline powder form as follows. We have taken SbCl (80mg) and added SeO2(60mg) to it followed by addition of (12ml) oleyl amine in a conical flask and kept on magnetic stirring for 5hours.Then, the solution was microwave heated in “CEM” made “Discover” research-based microwave for 10 minutes. The colour of the solution changed to black. After heating, the solution was cooled down and cleaned with water and ethanol several times. Finally, Sb2Se3 precipitate has been collected in the dry powder form. Preparation of the ink: The nanocrystalline powder solution of Sb2Se3 was mixed with SbCl3, which act as binding agent along with ethylene glycol (solvent) for the preparation of slurry. Screen printing process: Homemade screen-printing setup was used for the deposition of film as shown in Fig1. Glass is used as the substrate for the preparation of the film. After the preparation of the film, it isannealed for 4 hours at 1250C at atmospheric pressure and then left the film to cool down and dry so that it sticks to the glass substrate properly. After drying of the film, further measurement has been performed. FIGURE 1. Schematic illustration of overall fabrication process of screen-printing film. RESULTS and DISCUSSION XRD measurement has been performed for confirming the crystal structure of the synthesized sample using Bruker D8 Advance X-ray diffractometer The XRD spectra of nanocrystalline powder and film of Sb2Se3 has been taken and analyzed as shown in Fig1. Nanocrystalline powder XRD spectrum is matching with the JCPDS file00015-0861. From the spectra we observed that the crystal structure of Sb2Se3is orthorhombic with Pbnm Space group and the lattice parameter of the Sb2Se3 was found to be a =11.780Å b =11.633 Å c =3.985 Å. FIGURE 2. showing the Sb2Se3 XRD spectra of the (a) nanocrystalline line powder and (b) screen printed film. Crystal size of the Sb2Se3 nanocrystalline powder is calculated by using the Debye Scherrer formula: -