1：Experimental Design and Method Selection

The study focused on optimizing the layers thickness of a Ruddlesden–Popper perovskite for solar cell applications. The methodology included the synthesis of perovskite films with varying n values, characterization of their properties, and fabrication of solar cells to evaluate their performance.

2：Sample Selection and Data Sources

Perovskite films with n values ranging from 1 to 5 were prepared. The films were characterized using field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), ultraviolet-visible (UV-Vis) spectroscopy, and photoluminescence (PL) spectroscopy.

3：List of Experimental Equipment and Materials

Fluorine-doped tin oxide (FTO) conductive glasses, methylammonium bromide (MABr), formamidinium iodide (FAI), 5-ammonium valeric acid iodide (5-AVAI, S), lead (II) bromide (PbBr2), anhydrous ethanol, caesium iodide (CsI), tetra-n-octylammonium bromide (S'), titanium(IV) isopropoxide (TTIP), chlorobenzene, N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO). Equipment included Tescan MIRA 3 FE-SEM, Philips X’pert PW3020 XRD, Perkin Elmer Lambda 25 UV-Vis spectrometer, Avaspec 2048 TEC spectrophotometer, and Ivium CompactStat potentiostat/galvanostat.

4：Experimental Procedures and Operational Workflow

The perovskite solutions were prepared and deposited on FTO glasses coated with compact and mesoporous TiO2 layers. The films were treated with chlorobenzene as an anti-solvent and annealed. Solar cells were fabricated by depositing CuInS2 as a hole-transporting material and Au contacts.

5：Data Analysis Methods

The photovoltaic performance of the solar cells was evaluated using a solar simulator. Electrochemical impedance spectroscopy (EIS) was used to study the internal resistances and recombination dynamics. Data were analyzed using Zview software.