1：Experimental Design and Method Selection:

The study employs a combination of experimental techniques (UV-Vis absorption, photoluminescence, surface photovoltage, CELIV, ER-EIS, GIWAXS) and theoretical modeling to analyze the structural ordering and properties of PTB7 films with varying thicknesses. The theoretical part involves a drying model based on the Péclet number to explain skin formation during film drying.

2：Sample Selection and Data Sources:

PTB7 polymer films were prepared by spin coating from solutions in toluene and chloroform mixtures, with concentrations of 10 mg/mL and 20 mg/mL, cast onto quartz glass, glass/ITO, and n-doped silicon substrates. Film thicknesses ranged from 40 nm to 300 nm, controlled by spin speed and solution concentration.

3：List of Experimental Equipment and Materials:

Equipment includes a spin coater (Laurell WS-650-MZ-23NPP), profilometer (Dektak XT-E, Bruker), UV-Vis spectrometer (Lambda 1050, Perkin Elmer), fluorimeter (FSL 920, Edinburgh Instruments), cryostat (Optistat DN-V, Oxford Instruments), oscilloscope (OWON DS 7102 V), function generator (Agilent 33250 A), impedance analyzer (Solartron analytical model 1260), and GIWAXS system (Nanostar, Bruker). Materials include PTB7 polymer (Sigma Aldrich), solvents (toluene, chloroform), and substrates.

4：Experimental Procedures and Operational Workflow:

Films were spin-coated at speeds from 4500 to 1000 rpm, dried at 100°C in a nitrogen atmosphere. Thickness was measured with a profilometer. Absorption and PL spectra were recorded. SPV measurements were conducted with specific arrangements. CELIV was used for mobility measurements. ER-EIS was performed in a three-electrode cell with specific parameters. GIWAXS was done at an incident angle of 0.2°.

5：2°. Data Analysis Methods:

5. Data Analysis Methods: Data were analyzed using fitting procedures for SPV spectra to determine exciton diffusion length, CELIV for mobility calculation, ER-EIS for DOS determination, and GIWAXS for structural analysis. Theoretical modeling involved Péclet number analysis for drying behavior.