title: Synthesis and Characterization of Core-Shell SnO𝑥@Ag Nanowires and their Application in Environmentally Stable Transparent Electrodes
title: Synthese und Charakterisierung von Kern-Schalen SnO𝑥@Ag-Nanodrähten und ihre Anwendung in umweltstabilen transparenten Elektroden
Creators: name: Kalancha, Violetta
Publisher: name: Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU)
Year: 2024
Subjects: subject: silver nanowires, Transparent Conducting Electrodes, tin oxide

description: The potential of new materials such as silver nanowires (Ag NWs) is significant to match the performance of traditional materials, including the widely known indium tin oxide (ITO) for Transparent Conducting Electrodes (TCEs). ITO has several drawbacks, such as high cost, scarcity of indium, and brittleness. As a result of growing efforts in finding alternative materials to replace ITO, Ag NWs have emerged as a promising candidate. Using Ag NWs as TCEs offers several advantages, such as low cost, high electrical conductivity, flexibility, and excellent optical transparency. Therefore, Ag NWs can be a viable substitute for ITO and pave the way for the development of more efficient and cost-effective electronic devices. The primary objective of this thesis is to conduct a comprehensive investigation and evaluation of various methods for synthesizing Ag NWs and fabricating high-performance TCEs with competitive properties, such as high transparency over 92%, low sheet resistance of 10-20 Ω/sq, and maximum stability. This research focuses on optimizing the synthesis procedure to obtain Ag NWs with preferable properties for use in TCEs, as well as developing reliable and efficient methods for fabricating TCEs using the synthesized Ag NWs. This study will also evaluate the performance of Ag NWs as TCEs, including their stability and degradation behavior under various conditions, to determine their suitability for use in solar cells and other applications. Ultimately, this study aims to contribute to the ongoing efforts to facilitate the widespread application of Ag NW in modern electronic devices. The methods and materials used in this thesis were carefully chosen to ensure an easy and scalable approach to the synthesis process while maintaining control over the aspect ratio (AR) of the Ag NWs. To produce the Ag NWs, one-pot polyol and hydrothermal synthesis methods based on organic compounds were employed, which are known to be cost-effective and allow for the control of NW morphology. Furthermore, the influence of polyvinylpyrrolidone (PVP) molecular weight (MW) on the AR of Ag NWs was investigated, and it was found that increasing the MW of PVP from 55 kDa to 360 kDa resulted in a higher AR. In addition, the use of organic salts, such as tetrabutylammonium chloride (TBAC), was explored in the synthesis to determine their effect on the quality of the NWs in the final product. Combining these methods and materials provides a comprehensive approach to synthesizing Ag NWs with controlled size, which is crucial for their further application. Since a tin oxide (SnO𝑥) protective layer was found to be crucial in enhancing the stability of the Ag NWs, the wet chemistry approach to growing the protective layer on the Ag NWs was further investigated in this study. The purpose of this investigation was to determine the effect of the thickness of the SnO𝑥 shell on the performance of Ag NWs-based electrodes. To achieve this, the treatment time of the NWs at room temperature was varied to control the thickness of the SnO𝑥 shell within the range of 1.5-8 nm. Experimental results demonstrated that a SnO𝑥 layer thickness of 2 nm was found to produce the most optimal performance for the Ag NWs-based electrodes. Specifically, the deposition of a 2 nm SnO𝑥 shell was effective in preventing the oxidation and corrosion of the Ag NWs, which enhances the durability and longevity of the NWs. These findings demonstrate the importance of the SnO𝑥 shell thickness in enhancing the performance of Ag NWs-based electrodes and highlight the potential for further optimization of this protective layer to achieve even better results. Various techniques were employed to assess the stability of the SnO𝑥 layer and single NWs, including transmission electron microscopy (TEM) characterization and four-point measurements on a single nanowire. Cross-section and single-wire analysis were also performed for PVP and SnO𝑥 Ag NWs to allow for a more detailed examination of their properties. Welding and junction formation were analyzed to better understand the performance of the individual NWs. Additionally, the degradation behavior of PVP and SnO𝑥 silver nanowire electrodes was examined, including an investigation into the degradation effect of the SnO𝑥 layer at temperatures ranging from 200-500 ℃. This comprehensive analysis provides a deeper understanding of the properties and performance of Ag NWs with a SnO𝑥 protection layer, which can facilitate the design and fabrication of more stable and efficient devices. Overall, this research offers valuable insights into the optimization of Ag NWs with a SnO𝑥 protective layer and has important implications for developing of more reliable and durable electronic devices. In addition to investigating of the stability of the SnO𝑥 layer and single nanowires, this thesis also delves into the electrochemical properties of the Ag NWs. The potentiodynamic polarization technique was utilized to assess the electrochemical behavior of the nanowires, and the electrochemical corrosion of both PVP and SnO𝑥-coated Ag NWs electrodes was examined to evaluate their stability under different electrolytes.