Stretchable electrochromic devices based on embedded WO3@AgNW Core-Shell nanowire elastic conductors

Abstract

Stretchable electrochromic devices (SECDs) have steadily attracted widespread attention in wearable devices. However, the delamination of device architectures (electrochromic layer, conductive layer and substrate) and poor chemical stability of conductive layer (silver nanowires (AgNWs)) are the key issues to be resolved to ensure the practical applications of flexible electrochromic devices. Herein, we designed a flexible and stretchable WO3@AgNW-PrePDMS (Pre-cured Polydimethylsiloxane) electrode, through integrated and embedded design, to build a high-performance electrochromic device. The integration of electrochromic layer and conductive layer in the electrode is fabricated via a WO3@AgNW core–shell structure. And embed the core–shell structure into the flexible substrate PDMS to form WO3@AgNW-PrePDMS electrode. This electrode architecture can prevent the delamination of the stretchable electrode during bending tests. Moreover, WO3 as a shell structure protects the conductive material AgNW to prevent its oxidation and improve the stability of the conductive substrate. The WO3@AgNW-PrePDMS electrode displays outstanding electrochemical stabilities and excellent bi-functionalities (flexible conductive film and electrochromic electrode): high conductivity (12 Ω/sq) as flexible transparent conductive film and wide optical modulation range (ΔT = 72% at 550 nm) as electrochromic electrode. The stretchable WO3@AgNW-PrePDMS electrode can still maintain stable electrical conductivity (ΔR/R≈8.3% and 14%) and electrochromic performance (90% and 92% retention) after 20,000 bending cycles and stretching to 70%, indicating the excellent mechanical flexibility. The WO3@AgNW core–shell nanowire network electrodes with embedded structures can be a strong candidate for wearable electrochemical energy devices in the future.