CsI‐Antisolvent Adduct Formation in All‐Inorganic Metal Halide Perovskites

Abstract

The excellent optoelectronic properties demonstrated by hybrid organic/inorganic metal halide perovskites are all predicated on precisely controlling the exact nucleation and crystallization dynamics that occur during film formation. In general, high‐performance thin films are obtained by a method commonly called solvent engineering (or antisolvent quench) processing. The solvent engineering method removes excess solvent, but importantly leaves behind solvent that forms chemical adducts with the lead‐halide precursor salts. These adduct‐based precursor phases control nucleation and the growth of the polycrystalline domains. There has not yet been a comprehensive study comparing the various antisolvents used in different perovskite compositions containing cesium. In addition, there have been no reports of solvent engineering for high efficiency in all‐inorganic perovskites such as CsPbI3. In this work, inorganic perovskite composition CsPbI3 is specifically targeted and unique adducts formed between CsI and precursor solvents and antisolvents are found that have not been observed for other A‐site cation salts. These CsI adducts control nucleation more so than the PbI2–dimethyl sulfoxide (DMSO) adduct and demonstrate how the A‐site plays a significant role in crystallization. The use of methyl acetate (MeOAc) in this solvent engineering approach dictates crystallization through the formation of a CsI–MeOAc adduct and results in solar cells with a power conversion efficiency of 14.4%.

The Stabilization of Formamidinium Lead Tri‐Iodide Perovskite through a Methylammonium‐Based Additive for High‐Efficiency Solar Cells

“…To the best of our knowledge, in the works investigating perovskite composition by NMR, the analyzed compounds are precipitated powders, [7,[25][26][27] crystals, [7,26,28] or films produced by drop casting [25] or by spin coating combined with vacuum evaporation. [29] By using them, one can get a quite large amount of material that permits solid-state and/or liquid NMR investigations. However, the drawback of these techniques is that they deviate from the ones used for very-high-efficiency PSC fabrication.…”

Dimethylammonium: An A‐Site Cation for Modifying CsPbI3

“…e–h) Scanning electron microscope micrographs of Cs x DMA 1− x PbI 3 films with various x compositions, scale bars are 10 μm. The mixed composition films (e, f, and g) are treated with anisole during the spin‐coating process, but to make good films of pure CsPbI 3 , methyl acetate (MeOAc) is used [ 32 ] (shown clearly in the split panel of (h)).…”

Chemically Stable Black Phase CsPbI3 Inorganic Perovskites for High‐Efficiency Photovoltaics

“…Recently, Luther and co‐workers discovered that the formation of unique adducts between CsI and the antisolvent methyl acetate (MeOAc) could promote the nucleation process better than the PbI 2 –DMSO adduct to obtain high‐quality CsPbI 3 thin films. [ 67 ] This work demonstrated how the A‐site cation plays a significant role in crystallization during the solvent engineering process. Besides, some other small molecules, such as a π‐conjugated Lewis base 6TIC‐4F, which contains a strong electron‐donating core and two electron‐withdrawing units, were dissolved in the anti‐solvent to passivate the surface defects on the perovskite thin films, therefore improving the CsPbI 3 perovskite quality.…”