1：Experimental Design and Method Selection:

The study employed a novel precursor mixing method by combining PbI2:2CH3NH3I and PbCl2:3CH3NH3I in different ratios (denoted as Px, where x = 0,

2：07, 13, 29, 38, 47, 0) to control the formation of CH3NH3PbClThe perovskite films were fabricated using a one-step solution deposition method with spin-coating and thermal annealing. Sample Selection and Data Sources:

Precursor solutions were prepared with specific ratios, and perovskite films were deposited on ITO/PEDOT:PSS substrates. Data were collected from various characterization techniques.

3：List of Experimental Equipment and Materials:

Materials included ITO-coated glass, HI, CH3NH3, PbCl2, PbI2, PCBM, DMF, ethanol, chlorobenzene, etc. Equipment included Zeta sizer Nano-ZS for DLS, Carry 5000 for UV-vis, D2 PHASER for XRD, SEM for morphology, FLS 980 and Lifespec II for PL, Keithley 2400 for J-V measurements, QE-R3011 for IPCE, and IM6 electrochemical workstation for EIS.

4：Experimental Procedures and Operational Workflow:

Precursor solutions were mixed in a glovebox, spin-coated on substrates, annealed, and characterized. Device fabrication involved layering PEDOT:PSS, perovskite, PCBM, LiF, and Al.

5：Data Analysis Methods:

Data were analyzed using Image J for surface coverage, biexponential fitting for TRPL, equivalent circuit fitting for EIS, and standard photovoltaic parameter extraction for J-V curves.