Activation-enhanced four-state electrochromic mirrors with enhanced optical performance

Abstract

This study demonstrates a significant enhancement in reversible metal electrodeposition devices (RMEDs) through a systematic activation process using a silver‑copper electrolyte system. An electrode conditioning protocol employing a wider voltage range cyclic voltammetry (−3.5 V to 1.3 V) was developed to enable robust four-state optical switching beyond traditional transparent-mirror operation. The activation process resulted in a 63.6% increase in electrochemical activity and improved coloration efficiency, increasing from 43.2 to 54.7 cm²/C. Using an optimized step-voltage method, vivid red and blue color states were achieved, with transmittance modulation increasing from 26.2% to 58.9% for red color and from 56.9% to 63.0% for blue color after activation. The four-state device demonstrated excellent long-term stability, maintaining consistent optical performance over 6000 s of continuous cycling without degradation. This work establishes electrode activation as a key advancement for practical smart window applications, offering both aesthetic versatility through multicolor options and operational reliability for commercial use.