Formulation of concentrated and stable ink of silver nanowires with applications in transparent conductive films

Abstract

Silver nanowire transparent conductive films have been proposed as a promising candidate to replace indium tin oxide films for electronic applications. Stable ink with a high loading amount of silver nanowires is essential for the scale-up of the production of transparent conductive films considering the storage need due to separated procedures of nanowire synthesis and film formation. It is very hard to re-disperse the nanowires if irreversible aggregation happens during storage for coating. The paradox of stabilizing the concentrated nanowire ink and facile utilizing of the ink for highly conductive films with a low junction resistance at the joint points of organic stabilizer-capped silver nanowires has to be solved. A two-step method has been provided to overcome the difficulty in this work. First, a silver nanowire ink with the loading amount of 5 mg mL⁻¹ is formulated, which is stable for more than three months under normal conditions. The success in maintaining the long-term stability lies in applying an appropriate amount of surfactant and choosing organic solvents with appropriate mixing ratios to strengthen the interaction of the surfactant with the silver nanowires and to decrease the free energy through enthalpy of mixing silver nanowires into the solvent for aggregation prevention. Second, the concentrated ink at any time is simply washed a suitable number of times and diluted to a uniform dispersion for coating of TCFs with excellent optical and electrical performance, having a figure of merit σ_DC/σ_OP (ratio of the electrical conductance to optical conductance) as high as 228. The viability of treating silver nanowires in large quantity paves the way for real industrial applications.