2 methoxyethanol 2 me

2-Methoxyethanol (2-ME, 99.8%, Sigma-Aldrich), lead(II) iodide (PbI₂, 99.99% trace metals basis, TCI), lead(II) iodide (PbI₂, 99.999%, Alfa Aesar), formamidinium iodide (FAI, 99.99%, GreatCell Solar), methylammonium iodide (MAI, 99.99%, GreatCell Solar), benzylhydrazine hydrochloride (BHC, 95%, AmBeed), 4-fluoro-phenethylammonium iodide (4-F-PEAI, >99%, GreatCell Solar), L-α-phosphatidylcholine (LP, ≥99%, Sigma-Aldrich), 5%v/v MAH₂PO₂ (MAHP, synthesized in our lab), dodecylammonium iodide (N-DDAI, GreatCell Solar), dimethyl sulfoxide (DMSO, 99.9%, Sigma-Aldrich), ZnX₂ (99.99% and ≥98%, Sigma-Aldrich), zinc formate (98%, Alfa Aesar), zinc acetate (99.99%, Sigma Aldrich), zinc trifluoroacetate (Sigma Aldrich), zinc trifluoromethane sulfinate (95%, Sigma Aldrich), zinc trifluoromethane sulfonate (98%, Sigma Aldrich), choline chloride (CC, 99%, Sigma Aldrich), poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS, Clevios™ P VP AI 4083, Heraeus), poly(triarylamine) [PTAA, average M_n = 7000 to 10,000, Sigma-Aldrich], toluene (TL, 99.8%, Sigma-Aldrich), C₆₀ (Nano-C Inc), bathocuproine (BCP, 96%, Sigma-Aldrich), and Cu (99.99%, Kurt J Lesker) were purchased and used as received.

Carboxylic acid cation-exchange resin WAC-gel (WACG-HP, gel type, hydrogen form) and WAC-MP (WACMP, macroporous type, hydrogen form) and sulfonic acid cation-exchange resin SAC-MP (SACMP-H, macroporous type, hydrogen form) were purchased from ResinTech Inc. Sulfonic acid cation-exchange resin SAC-gel (Amberlite^® IRC120 H, gel type, hydrogen form), Lead(II) iodide (99%), PTAA (average Mn 7000–10,000), bathocuproine (BCP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), 2-methoxyethanol (2-ME), 1,2-Dichlorobenzene, toluene, isopropyl alcohol, phenylethyl ammonium chloride, and Pb standard solution (1000 ± 2 ppm) were purchased from Sigma-Aldrich. Lead(II) iodide (99.99%, trace-metal basis) was purchased from TCI America. Formamidinium iodide (FAI) and formamidinium chloride were purchased from GreatCell Solar. C₆₀ was purchased from Nano-C Inc. Copper (Cu) and chromium (Cr) for thermal evaporation were purchased from Kurt J. Lesker company.

The SnS seed ink was prepared by weighing 3 mmol of SnCl₂·2H₂O (Sigma Aldrich, 98%, USA) and 3 mmol of sulfur powder (Sigma Aldrich, 99.98%, USA) in a N₂‐filled glovebox. 2 mL of 2‐mercaptoethanol (Sigma Aldrich, 99%, USA) and 8 mL of ethylenediamine (Sigma Aldrich, 99.5%, USA) were added to dissolve the precursor mixture. Then, 10 mL of 2‐methoxyethanol (2ME, Sigma Aldrich, ≥99.0%, USA) was added, followed by stirring and aging at 60 °C for overnight. Three different SnS absorber inks were prepared by using different sulfur precursor and the identical amount of SnCl₂·2H₂O (15 mmol). 0.76 g of thiourea (10 mmol, Sigma Aldrich, 98%, USA), 0.75 g of thioacetamide (10 mmol, Sigma Aldrich, 99.0%, USA), and 1.21 g of L‐cysteine (10 mmol, Sigma Aldrich, 97%, USA) were separately dissolved in 10 mL of 2ME as well as the addition of SnCl₂·2H₂O, followed by stirring at 60 °C for 30 min in a N₂‐filled glovebox.