Highly Stable Ag-Au Core-Shell Nanowire Network for ITO-Free Flexible Organic Electrochromic Device

Solid and flexible electrochromic (EC) devices require a delicate design of every component to meet the stringent requirements for transparency, flexibility, and deformation stability. However, the electrode technology in flexible EC devices stagnates, wherein brittle indium tin oxide (ITO) is the primary material. Meanwhile, the inflexibility of metal oxide usually used in an active layer and the leakage issue of liquid electrolyte further negatively affect EC device performance and lifetime. Herein, a novel and fully ITO-free flexible organic EC device is developed by using Ag-Au core-shell nanowire (Ag-Au NW) networks, EC polymer and LiBF4/propylene carbonate/poly(methyl methacrylate) as electrodes, active layer, and solid electrolyte, respectively. The Ag-Au NW electrode integrated with a conjugated EC polymer together display excellent stability in harsh environments due to the tight encapsulation by the Au shell, and high area capacitance of 3.0 mF cm(-2) and specific capacitance of 23.2 F g(-1) at current density of 0.5 mA cm(-2). The device shows high EC performance with reversible transmittance modulation in the visible region (40.2% at 550 nm) and near-infrared region (-68.2% at 1600 nm). Moreover, the device presents excellent flexibility (>1000 bending cycles at the bending radius of 5 mm) and fast switching time (5.9 s).

Automated summary

The design of flexible electrochromic devices requires careful consideration of each component for improved performance and stability. A novel flexible organic EC device using Ag-Au core-shell nanowire networks, EC polymer, and solid electrolyte shows excellent stability and high capacitance, with reversible transmittance modulation in visible and near-infrared regions. This device also demonstrates outstanding flexibility and fast switching time.