Integrating exceptional visible modulation, near-infrared shielding and energy storage in an all-solid-electrochromic bilayer device

Abstract

A generic strategy of incorporating diverse functions in electrochromic dynamic windows is presented by sensibly choosing the individual layers of a bilayered active electrode. Here, all-solid electrochromic devices (ECD) with a remarkably high visible modulation (60–80%) and superior near-infrared (NIR) shielding performance (>90% full scale) were fabricated by simple solution-processing. The concept is demonstrated by selecting materials with identical chemical composition, i.e., porous amorphous-WO3 (a-WO3) coated on top of polycrystalline WO3·H2O nanosheets. These ECDs show four distinct voltage-selective modes in the ± 2.8 V range for enhanced privacy and energy saving. The IR modulation efficiency (IRME) of the devices stands at a record ~85%, with an outstanding solar modulation efficiency (SME) of ~63%. The initial energy storage estimations for the ECDs revealed superior volumetric stored charge density of ~400 Ccm−3@ 10 mVs−1, which is excellent for secondary energy sourcing. The fabricated EC glasses (with 50% usage) could directly save ~165 kWhm-2 yr-1 worth of energy by equating the energy-saving and generation. With reflected radiation reduction, the total saving may surpass the total energy generation from standard Si-Solar cells (~18% efficiency) of equal areal coverage.