1：Experimental Design and Method Selection

The study proposes CdSe/ZnS quantum dots as a new electron transporting layer (ETL) in planar perovskite solar cells (PSCs) for the first time, with down-shifting property. The fabrication involves depositing a thin layer of CdSe/ZnS QDs as an ETL using a solid-state ligand exchange method.

2：Sample Selection and Data Sources

CdSe/ZnS QDs with green (520 nm) and red (640 nm) emissions were used as ETLs in the PSCs. Methylammonium lead triiodide (MAPbI3) perovskite was employed with a bandgap of 1.55 eV.

3：List of Experimental Equipment and Materials

Indium-coated tin oxide (ITO) glasses, titanium diisopropoxide bis(acetylacetonate), CdSe/ZnS QDs (Mesolight), methylammonium iodide, PbI2, Spiro-OMeTAD, Li-TFSI, 4-tert-butylpyridine, gold.

4：Experimental Procedures and Operational Workflow

The ITO glasses were cleaned and treated with oxygen plasma. The TiO2 compact layer was deposited and annealed. CdSe/ZnS QDs were deposited using a solid-state ligand exchange technique. Perovskite film was deposited using a layer-by-layer vacuum approach. The hole transporting layer (HTL) was spin-coated, and gold electrodes were thermally evaporated.

5：Data Analysis Methods

Characterization included scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy, UV-visible spectroscopy, time-resolved PL (TRPL), and ultraviolet photoelectron spectroscopy (UPS). Device performance was measured using a xenon lamp under AM1.5G standard condition.