Complementary electrochromic device via a scalable solution process: a step towards affordable and energy-efficient smart windows

Abstract

Amidst the mounting energy crisis and the pressing need to combat global warming, efficient energy utilization within buildings has emerged as a critical imperative, with buildings currently contributing to 40% of global energy consumption. Electrochromic devices (ECDs), particularly smart windows, have garnered significant attention as a sustainable solution, offering user-controlled light transmission. This manuscript explores the development of a complementary electrochromic device (CECD) utilizing WO₃ and NiO electrodes fabricated via pneumatic spray-pyrolysis. By optimizing deposition parameters, exceptional visibility modulation is achieved, surpassing previous reports related to CECD developed using spray pyrolysis. The WO₃ cathode exhibits high optical modulations of 66% and 71.5% at 550 nm and 700 nm wavelengths, with rapid response and recovery times. Meanwhile, the NiO anode demonstrates complementary electrochromic properties with optical modulations of 51.5% and 44.5% at the same wavelengths. The resulting CECD, fabricated on a 5 × 5 cm² scale, showcases optical modulations of 67% and 59% at 550 nm and 700 nm, with remarkable stability over 400 cycles of switching. Furthermore, the device exhibits a high areal capacitance of 2.2 mF cm⁻² and coloration efficiencies of 81.59 cm² C⁻¹ and 102.7 cm² C⁻¹ at 550 nm and 700 nm, respectively. This study presents a facile and scalable fabrication approach for electrochromic electrodes, offering promising prospects for solution-based methods in electrochromic energy storage applications.