Proton transfer from methylammonium (CH₃NH₃⁺) to dimethylsulfoxide (DMSO), a common Lewis-base solvent, initiates the production of ammonium (NH₄⁺) and dimethylammonium ([CH₃]₂NH₂⁺). We propose two parallel reaction pathways initiated by this proton transfer. Using DMSO-d₆ to elucidate reaction schemes, we demonstrate that protonation is followed either by methyl group transfer between the resulting CH₃NH₂ and residual CH₃NH₃⁺, or by transmethylation to CH₃NH₂ from DMSOH⁺. The former reaction yields NH₄⁺ and (CH₃)₂NH₂⁺ and is the dominant pathway at processing relevant temperatures; the latter yields (CH₃)₂NH₂⁺ in addition to methylsulfonic acid and dimethylsulfide. In the preparation of hybrid organic–inorganic perovskite (HOIP) thin films for photovoltaic applications, the substitution of CH₃NH₃⁺ with NH₄⁺ and (CH₃)₂NH₂⁺ in the HOIP crystal results in deviations from the tetragonal structure expected of phase-pure CH₃NH₃PbI₃, with a deleterious effect on the absorptivity of the resulting films. These results emphasize the importance of elucidating the under-appreciated precursor/solvent reactivity, the products of which, when incorporated into the solid state, can have profound effects on HOIP composition and structure, with a commensurate impact on macroscopic properties and device performance.

中文翻译：

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酸催化反应将DMSO活化为钙钛矿前体油墨中的试剂

质子从甲基铵（CH ₃ NH ₃ ⁺）转移到二甲基亚砜（DMSO）（一种常见的路易斯碱溶剂），引发了铵（NH ₄ ⁺）和二甲基铵（[CH ₃ ] ₂ NH ₂ ⁺）的生产。我们提出了由该质子转移引发的两个平行反应途径。使用DMSO- d ₆阐明反应方案，我们证明质子化之后是在所得CH ₃ NH ₂和残留的CH ₃ NH ₃ ^+之间进行甲基转移，或通过甲基化转变为CH ₃ NH₂来自DMSOH ⁺。前者反应生成NH ₄ ⁺和（CH ₃）₂ NH ₂ ^+，并且是处理相关温度下的主要途径。后者除了产生甲基磺酸和二甲基硫醚外，还产生（CH ₃）₂ NH ₂ ⁺。在杂化有机-无机钙钛矿（HOIP）薄膜用于光伏应用，CH的取代的制备₃ NH ₃ ⁺与NH ₄ ⁺和（CH ₃）₂ NH ₂ ⁺HOIP晶体中的α会导致偏离纯相CH ₃ NH ₃ PbI ₃预期的四方结构，从而对所得薄膜的吸收率产生有害影响。这些结果强调了阐明未被充分认识的前体/溶剂反应性的重要性，当将其产物掺入固态时，其产物可对HOIP组成和结构产生深远影响，并对宏观性能和器件性能产生相应影响。