Fabrication of Energy-Efficient Smart Windows Using All-Solution-Processed Interconnected Ag Transparent Electrodes

Transparent conducting electrodes (TCEs) are essential for optoelectronic devices, including sensors, displays, solar cells, and smart windows. Tin-doped indium oxide (ITO), the most widely used transparent conductor, offers high optical transmittance and low sheet resistance but suffers from high material cost due to its scarcity. This work reports a scalable, complete solution-based approach for fabricating silver (Ag) TCEs from Ag thin films prepared via Tollens' reagent. The method combines electrospun polymer fibers as sacrificial masks followed by selective wet-chemical etching of thin films. The selective removal of the exposed Ag layer, followed by the dissolution of the polymer fiber template, yields a highly interconnected Ag network with seamless junctions and tunable optoelectronic properties. By modulating the width and density of the electrospun fibers, optical transmittance and sheet resistance were fine-tuned between 45 and 93% and 13-427 Ω/□, respectively. A thin layer of polydimethylsiloxane (PDMS) was coated as an encapsulation layer to enhance their mechanical stability. The fabricated Ag/PDMS electrodes were employed as a transparent heater to achieve a steady state temperature (∼74 °C) with low input voltages (2.5 V). In addition, the Ag/PDMS heater was effectively used to modulate the transition of hydroxypropyl methylcellulose (HPMC)-based phase-changing smart windows between transparent and opaque states, thereby enabling on-demand light and heat transmission through them. The current work demonstrates a simple, scalable, complete solution-based, lithography-free TCE fabrication technique at ambient conditions for promising next-generation flexible optoelectronics applications.