Lead halide complexes formed during the fabrication of perovskite (CH 3 NH 3 PbI 3 )-based solar cells were examined by single-crystal X-ray diffraction analysis. Based on the observed results, the fabrication protocol using a sequential deposition method was optimized to reproducibly provide highly efficient solar cells with power conversion efficiencies of more than 10%. ) and vapor deposition processes, 7 have been reported for the formation of perovskite layers. In this work, we used a sequential deposition method and examined the influence of the purity of the starting materials on the formation of the resulting perovskite layers in solar cells with high PCEs. Moreover, we report the results of single-crystal X-ray diffraction analyses conducted on lead halide complexes, which are potentially formed during the production process. Based on the results obtained, the fabrication protocol for the solar cells was optimized. We found that for the reproducible fabrication of highly efficient perovskite solar cells, the water content of lead iodide (PbI 2 ) as the starting material is crucial. Our optimized method uses dehydrated PbI 2 and thus enables the highly reproducible fabrication of solar cells with PCEs of more than 10%.To minimize the influence of water and oxygen, we prepared the perovskite and hole-transporting layers in an inert glovebox (Ar; H 2 O and O 2 , <0.1 ppm) using dehydrated (H 2 O, <8 ppm) N,N-dimethylformamide (DMF), 2-propanol, and chlorobenzene. Otherwise, the solar cells were fabricated according to literature procedures.6 Patterned transparent conducting oxide substrates (FTO, 25 mm © 25 mm) were covered with a compact TiO 2 layer by spray pyrolysis of bis(acetylacetonato)titanium diisopropoxide in ethanol (0.05 M) at 450°C.6,15 Subsequent spin-coating of an ethanol suspension of a TiO 2 paste (PST-18NR, TiO 2 paste:ethanol = 1:3.5 wt ratio) resulted in the deposition of ca. 200 nm-thick-mesoporous films of TiO 2 nanoparticles (particle diameter: ca. 20 nm). In an Ar-filled glovebox, PbI 2 was then introduced into the TiO 2 nanopores by spin-coating a solution of PbI 2 in DMF (1.01.1 M) at 70°C. Upon drying (70°C, 1 h), the films turned to deep yellow. Afterwards, the films were dipped for 20 s in a 0.06 M solution of CH 3 NH 3 I in 2-propanol. During this process, the color of the films turned to red-black from the corner of the square substrates (see movie in the SI
16). This may be attributed to the slightly nonhomogeneous distributions of the PbI 2 loadings on the substrate surface during the spin-coating process. The films were quickly rinsed with 2-propanol and dried (70°C, 30 min). The hole-transporting layer was deposited on the perovskite layer by spin-coating a solution of 2,2¤,7,7¤-tetrakis(N,N-di-p-methoxyphenylamine)-9,9¤-spirobifluorene (spiro-OMeTAD) in chlorobenzene (0.058 M) containing 4-tert-butylpyridine (0.19 M) and lithium bis(trifluoromethylsulfonyl)imide (0.031 M) as well as tris[2-(1H-pyrazol-1-yl)-4-tert-butylpyridine]cobalt(III) tris[bis(trifluoromethylsulfonyl...
