Methylammonium iodide

Indium tin oxide substrates
(ITO), methylammonium iodide (MAI, 98%), and 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene
(Spiro-MeOTAD, 99%) were purchased from Ossila. Isopropyl alcohol
(IPA, 99.7%), anhydrous dimethylformamide (DMF, 99.8%), dimethyl sulfoxide
(DMSO, 99.8%), acetonitrile (99.8%), chlorobenzene (99.9%), 4-tert-butylpyridine (4-tBP, 96%), lithium
bis(trifluoromethanesulfonyl)imide (LiTFSI, 99.95%), tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)-tris(bis(trifluoromethylsulfonyl)imide)
(FK209, 98%), and pHEMA were purchased from Sigma-Aldrich. Tin (IV)
oxide (SnO₂), Hellmanex III detergent, and lead iodide
(PbI₂) were purchased from Alfa Aesar.

All materials and solvents were used as received without any further purification. MeO‐2PACz (>98%), 2PACz (>98%), and PbI₂ (99.99% trace metals basis) were purchased from Tokyo Chemical Industry. Methylammonium iodide (MAI, >99.9%), 20 mm x 15 mm ITO (≈20 Ω □⁻¹) and TEC10 FTO (11–13 Ω □⁻¹) were purchased from Ossila. All solvents and remaining materials including C₆₀ (sublimed, 99.99%) and BCP (sublimed, 99.99%) were purchased from Sigma‐Aldrich unless otherwise stated. Substrates were patterned using a zinc and acid (4 m, HCl) etch, then cleaned by subsequent ultrasonication in diluted Helmanex solution, boiling deionized water, acetone, and isopropanol (IPA) consecutively. Substrates were then dried under a flow of N_2, and UV ozone treated for at least 15 min immediately prior to further processing. All perovskite solutions were filtered into a clean, glass vial through a 0.2 µm polytetrafluoroethylene (PTFE) filter prior to deposition. Note that a small increase in device performance was observed when the HTL was fabricated one day prior to processing the perovskite layer.

Prepatterned eight-pixel
ITO glass, methylammonium iodide (MAI; 98%), formamidinium iodide
(FAI; 98%), 2,2′,7,7′-tetrakis[N,N-bis(4-methoxyphenyl)amino]-9,9′-spirobifluorene
(spiro-OMeTAD; 99.0%) were purchased from Ossila. 1-Butanol (99.8%),
titanium diisopropoxide bis(acetylacetonate) (75 wt % in isopropanol),
tantalum(V) butoxide (99.99%), lead iodide (PbI₂; 99.9985%),
lead(II) chloride (PbCl₂; 99.999%), lead(II) thiocyanate
(Pb(SCN)₂; 99.5%), ethyl acetate (99.8%), cesium iodide
(CsI; 99.999%), dimethyl sulfoxide (DMSO; 99.9%), dimethylformamide
(DMF; 99.8%), chlorobenzene (99.9%), 4-tert-butylpyridine
(tBP; 98%), bis(trifluoromethane)sulfonimide lithium salt (LiTFSI;
99.95%), tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(III) tris[bis(trifluoromethane)sulfonimide]
(KF209; 98%), and acetonitrile (99.8%) were purchased from Sigma-Aldrich.
Hellmanex III detergent was purchased from Alfa Aesar.