1：Experimental Design and Method Selection:

The study involves fabricating a four-layer electrochromic device with ITO, Nafion membrane, and WO3 layers. WO3 and ITO thin films are deposited using reactive DC magnetron sputtering at room temperature. The coloration efficiency is analyzed based on Beer-Lambert's law with a modified formula using volume charge density.

2：Sample Selection and Data Sources:

Soda lime glass substrates are used. WO3 thickness is varied from 44nm to 200nm by changing deposition times (30, 45, 60, 90, 120 minutes), labeled as 30-G, 45-G, 60-G, 90-G, 120-G.

3：List of Experimental Equipment and Materials:

Equipment includes reactive DC magnetron sputtering system with Advanced Energy power supply (MDX 1KW), profilometer (Bruker 3D Non-contact Profiler), X-ray diffractometer (Xpert Pro with Cu Kα radiation), Raman spectrometer (Horiba Jobin Yvon Lab Ram with 532nm excitation), UV-Vis spectrophotometer (Cary 60), cyclic voltammetry and chronoamperometry setup (Biologic SP-300), SEM. Materials include metallic tungsten target (

4：9% pure, size 380mm x 127mm), ITO target (In:

Sn::90:10, size 380mm x 127mm), Nafion 117 membrane (commercially procured, 183μm thick), argon and oxygen gases.

5：Experimental Procedures and Operational Workflow:

Clean glass substrates are used. ITO films (400nm) are deposited first. WO3 films are deposited on ITO with varying thicknesses. Nafion membrane is placed on WO3 using Nafion solution glue and pressed mechanically. Another ITO-coated glass is pressed on top. Devices are characterized using XRD, Raman, optical transmission, cyclic voltammetry, and chronoamperometry.

6：Data Analysis Methods:

Thickness measured by profilometry. Optical band gap evaluated using Tauc plot. Coloration efficiency calculated from transmission changes and charge intercalation using modified Beer-Lambert's law. Statistical analysis of reproducible results within experimental error.