Polyol법에 의한 Silver nanowire 합성의 최적화와 이의 투명전도성 박막에서의 응용

Abstract

Silver nanowire (Ag-NW) film meets the requirements of transparent conducting electrodes for many applications and can be an immediate ITO replacement for touch panel electrodes. In order to fabricate high-quality Ag-NW transparent conducting films, the morphology of Ag-NW that has thin thickness (< 100 nm) and long length (>10 µm) is critical. One of the most promising methods to synthesize Ag-NW is a so-called polyol method where polyvinylpyrrollidone (PVP) and ethylene glycol are used as a template for one-dimensional growing and a reducing agent of silver precursor, respectively. In this thesis we have investigated the critical factors for synthesizing thinner and longer Ag-NW in two different types of polyol methods, self-seeding and pre-seeding methods. The effects of the various control agents such as NaCl, KCl, CuCl2·2H2O and KBr and the final synthetic temperature were investigated in the self-seeding method where Ag-NW grew from Ag-precursor itself as the reaction temperature increased. In the Pre-seeding method where Ag nanoparticle was first synthesized at a constant temperature and served as a seed for growing Ag-NW the effects of the mixing rate of Ag-precursor, molecular weight of PVP and the ratio of PVP vs Ag precursor were investigated. The most desirable Ag-NW was reproducibly obtained from the self-seeding method where both NaCl and KBr were used as control agents. The morphology of the synthesized Ag-NW is of about 40-50 nm in thickness and 15-20 µm in length. Utilizing the optimized Ag-NW and a polymer binder Ag-NW transparent conducting films were prepared on the flexible substrate of polyethylene terephthalate and its optical and electrical properties were characterized. The prepared Ag-NW film showed 85-90% of visible light transmittance, 2.5-4% of haze and 35-110 Ω/sq of sheet resistance depending on the thickness of the film.