Novel Transparent TiO2/AgNW-Si(NH2)/PET Hybrid Films for Flexible Smart Windows

The application of flexible indium tin oxide (ITO)-free electrochromic devices (FCDs) has always been a research hotspot in flexible electronics. Recently, a silver nanowire (AgNW)-based transparent conductive film has raised great interest as an ITO-free substrate for FCDs. However, several challenges, such as the weak binding of AgNWs to the substrate, high junction resistance, and oxidation of AgNWs, remain. In this paper, a novel method for surface modification of AgNWs with N-aminoethyl-gamma-aminopropyltrimethoxysilane [Si(NH2)] solution is proposed to enhance the bonding with the flexible substrates and the active materials, thereby inhibiting the delamination of AgNWs from the substrate and reducing the high junction resistance between nanowires. The TiO2/AgNW-Si(NH2)/poly(ethylene terephthalate) (PET) films show outstanding mechanical properties, of which the resistance remains almost unchanged after mechanical bending of 5000 cycles (Delta R/R-0 approximate to 3.6%) and repeated peeling off cycles with 3M tape 100 times (Delta R/R-0 approximate to 6.0%). In addition, we found that the oxygen-containing groups on the TiO2/AgNW-Si(NH2)/PET surface form hydrogen bonds with the TiO2 sol, resulting in tight contact between the TiO2 sol and the AgNWs, which prevents the AgNWs from oxidation. As a result, the TiO2/AgNW-Si(NH2)/PET film exhibited long-time aging (Delta R/R-0 approximate to 4.9% in the air for 100 days) stability. A FCD was constructed with the TiO2/AgNW-Si(NH2)/PET film, which showed excellent electrochromic performance (94% retention) after 5000 bending cycles, indicating high stability and mechanical flexibility. These results present a promising solution to the transparent conductive films for flexible energy devices.

Automated summary

This article presents a method to improve the silver nanowire transparent conductive film by surface modification and hydrogen bonding, which enhances the bonding strength with the flexible substrate, inhibits oxidation, and reduces the junction resistance. The resulting film exhibits excellent mechanical properties and stability, making it a promising solution for transparent conductive films in flexible energy devices.