Rapid synthesis of ultra-long silver nanowires for tailor-made transparent conductive electrodes: proof of concept in organic solar cells

Abstract

Rapid synthesis of ultralong silver nanowires (AgNWs) has been obtained using a one-pot polyol-mediated synthetic procedure. The AgNWs have been prepared from the base materials in less than one hour with nanowire lengths reaching 195 μm, which represents the quickest synthesis and one of the highest reported aspect ratios to date. These results have been achieved through a joint analysis of all reaction parameters, which represents a clear progress beyond the state of the art. Dispersions of the AgNWs have been used to prepare thin, flexible, transparent and conducting films using spray coating. Due to the higher aspect ratio, an improved electrical percolation network is observed. This allows a low sheet resistance (RS = 20.2 Ω/sq), whilst maintaining high optical film transparency (T = 94.7%), driving to the highest reported figure-of-merit (FoM = 338). Owing to the light-scattering influence of the AgNWs, the density of the AgNW network can also be varied to enable controllability of the optical haze through the sample. Based on the identification of the optimal haze value, organic photovoltaics (OPVs) have been fabricated using the AgNWs as the transparent electrode and have been benchmarked against indium tin oxide (ITO) electrodes. Overall, the performance of OPVs made using AgNWs sees a small decrease in power conversion efficiency (PCE), primarily due to a fall in open-circuit voltage (50 mV). This work indicates that AgNWs can provide a low cost, rapid and roll-to-roll compatible alternative to ITO in OPVs, with only a small compromise in PCE needed.

Comprehensive Synthesis Study of Well-Dispersed and Solution-Processed Metal Nanowires for Transparent Heaters

“…For all subsequent syntheses, the process time was kept at 30 min to ensure a completed wire growth. This time compares well or is even shorter than studies that report a duration of 30 min [28], 60 min [6,29,30], and 120 min [31] for their standard process.…”

“…Finally, for the synthesis section of this work, the effect of the addition of the halide KCl was studied. So far, a few studies have presented the use of halides such as KBr for the synthesis of AgNWs and reported a reduction in diameter [28,31,42,46,47]. For adding different concentrations of KCl (3-15 wt.%, see supporting information Figure S-6), we have also observed a modulation in diameter, which lies in the range of 78-114 nm.…”

“…For this study, a careful temperature calibration was performed using a Pt100 thermoresistor that is placed in the heated EG solution to give the exact temperature. The occurrence of an optimum growth temperature was reported earlier [28,33] and can be explained as follows: the higher the process temperature the higher the reduction of Ag + -ions to neutral Ag 0 -atoms that can contribute to the wire formation faster and lead to longer wires. However, the binding of the capping agent to the (111) plane that should be reserved exclusively for Ag 0 -atoms is also enhanced for increased temperatures [31].…”

“…After the effect of stirring during the growth was studied, the influence of the precursor to capping agent weight ratio, that is, the AgNO 3 to PVP weight ratio, was investigated. For the capping agent, we chose PVP with an average molecular (MW) weight of 360 kgmol −1 , referred to as PVP360k in the following, which is frequently reported in the literature for the polyol-based synthesis of AgNWs [28,34,[38][39][40]. Besides, for PVP360k, numerous synthesis protocols have been proposed that employed PVPs with a different average MW that in turn corresponds to a different average chain length.…”

Effective Synthesis and Recovery of Silver Nanowires Prepared by Tapered Continuous Flow Reactor for Flexible and Transparent Conducting Electrode

“…Silver nanowires (AgNWs) have been extensively studied during past years. They exhibit high conductivity(~105 Scm´1) without any detrimental effects to their high transparency (>90%) [11]. Regarding the synthesis of silver nanowires several methods have been reported including hard-template [12,13] and soft template synthesis [14].…”