Triphenylphosphine oxide

Methyldiphenylphosphine oxide, phenylphosphonic dichloride, triphenylphosphine oxide, and triethylphosphine oxide were purchased from Sigma-Aldrich and were used without further purification. Chloroform-d (CDCl3, 99.8 atom % D, Eurisotop), for use in NMR spectroscopy as the solvent, was also used as received.

Lead iodide (II) (PbI₂, 99.999%), 1‐octadecene (technical grade 90%), oleic acid (technical grade 90%), cesium carbonate (Cs₂CO₃, 99.99%), n‐hexane (anhydrous), n‐octane (99%), toluene (anhydrous), 2‐pentanol (2‐PeOH, 99%), lithium bis(trifluoromethylsulfonyl)imide (Li‐TFSI, 98%), and 2‐n‐pentylpyridine were purchased from Alfa Aesar. Oleylamine (technical grade 70%), sodium acetate (NaOAc, 99.995%), chlorobenzene (anhydrous 99.8%), and acetonitrile (99.8%), triphenylphosphine oxide (TPPO, 98%), were purchased from Sigma–Aldrich. Phenethylammonium iodide (PEAI) was purchased from GreatcellSolar. 2,20,7,70‐Tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,90‐spirobifluorene (Spiro‐OMeTAD, ≥ 99.5%) was purchased from Lumtec. Methyl acetate (MeOAc, ≥ 99.5%) and ethyl acetate (EtOAc, ≥ 99.5%) were purchased from Duksan. TiO₂ precursor solution (0.15 M), and TiCl₄ aqueous solution (2 M) were purchased from Sharechem. Phenyl‐C61‐butyric acid methyl ester (PCBM, ≥99.95%) was purchased from 1‐Materials.