1：Experimental Design and Method Selection:

The study involved the preparation of keratin films from aqueous solution with glycerol as a plasticizer, followed by characterization of their morphology, structure, thermal, and mechanical properties. The impact of solvents and thermal annealing was investigated to mimic device fabrication conditions.

2：Sample Selection and Data Sources:

Keratin was extracted from Merino wool. Films were prepared by casting keratin aqueous solution containing glycerol.

3：List of Experimental Equipment and Materials:

Materials included PEDOT:PSS, P3HT, PC61BM, and other solvents. Equipment used included a Perkin Elmer Lambda 650 UV–Vis spectrophotometer, Zeiss EVO LS 10 LaB6 scanning electron microscope, and a Keithley 236 source-measure unit for photovoltaic characterization.

4：Experimental Procedures and Operational Workflow:

Films were characterized for transparency, morphology, and mechanical properties. Organic solar cells were fabricated on the keratin films and their performance was evaluated.

5：Data Analysis Methods:

Data were analyzed using ORIGIN 8.1 software for FTIR spectra fitting. Mechanical properties were determined by tensile tests, and photovoltaic performance was evaluated under standard illumination.