1：Experimental Design and Method Selection:

The study employed single-step and two-step solution deposition methods to fabricate CH3NH3PbI3 perovskite thin films. The structure and morphology were controlled by varying concentration, annealing temperatures, and dip coating times. The Tauc equation was used to determine optical band gaps from UV-Vis absorbance data, and the four-point probe method was used for electrical characterization.

2：Sample Selection and Data Sources:

Thin films were prepared on glass slides using lead iodide (PbI2), N,N-Dimethylformamide (DMF), isopropanol, and methyl ammonium iodide (MAI). Samples were prepared with different concentrations (e.g.,

3：015g/mL, 02g/mL), annealing temperatures (80°C, 150°C, 170°C), and dip coating times (16, 48, 96 hours). List of Experimental Equipment and Materials:

Equipment included a Zeiss Axio 100 Optical Microscope, Cary 60 UV-Vis spectrophotometer (Agilent Technologies), and Jandel four-point probe setup. Materials included PbI2 (

4：8%, Sigma Aldrich), DMF (8%, Sigma Aldrich), isopropanol (8%, Sigma Aldrich), and MAI (8%, Solaronix). Experimental Procedures and Operational Workflow:

For single-step method, CH3NH3PbI3 solution was drop-cast on glass slides and annealed at varying temperatures. For two-step method, PbI2 films were drop-cast, dried, and dipped in MAI solution for varying times. Morphology was examined via optical microscopy, optical properties via UV-Vis spectroscopy, and electrical properties via four-point probe measurements.

5：Data Analysis Methods:

Optical band gaps were calculated using Tauc plots. Sheet resistance and resistivity were calculated using standard four-point probe equations. Activation energies were determined from Arrhenius plots of sheet resistance versus temperature.