1：Experimental Design and Method Selection:

The study developed an annealing-free, dopant-free, and amorphous tungsten oxide as an electron transport layer by vacuum evaporation for flexible perovskite solar cells. The thickness of the amorphous tungsten oxide layer was varied to study its effect on the solar cell's performance.

2：Sample Selection and Data Sources:

The amorphous tungsten oxide films were fabricated on ITO glass substrates by vacuum thermal evaporation method. The thickness of the films was monitored by an in-situ thickness detection system.

3：List of Experimental Equipment and Materials:

VZZ-400 thermal evaporation equipment was used for the deposition of tungsten oxide films. WOx powder (Aladdin, 99.9%) was used as the source material.

4：9%) was used as the source material. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: The ITO glass substrates were cleaned before the deposition of the electron transport layer. The WOx powder was evaporated at a rate of 0.5 ?/s onto ITO glass substrates under specific pressure and power conditions. The thickness of the films was controlled to be 15, 30, and 50 nm, respectively.

5：5 ?/s onto ITO glass substrates under specific pressure and power conditions. The thickness of the films was controlled to be 15, 30, and 50 nm, respectively. Data Analysis Methods:

5. Data Analysis Methods: The performance of the solar cells was evaluated through various characterizations including X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM), and electrical impedance spectroscopy (EIS).