Methylammonium Polyiodides: Remarkable Phase Diversity of the Simplest and Low-Melting Alkylammonium Polyiodide System

Newly discovered methylammonium polyiodides (MAIx) are unique precursors for innovative solvent-free technologies in perovskite photovoltaics because MAIx are liquids at room temperature and demonstrate high chemical reactivity. We investigated the features of an MAI-I2 system and built up a first phase diagram in wide temperature and composition ranges using data from differential scanning calorimetry, single-crystal X-ray diffraction, and visual thermal analysis. The phase diagram has been found to differ drastically from that of any related systems owing to the unique propensity of methylammonium toward forming a diversity of polyiodides with complicated crystal structures, namely, MAI2, MAI2.67, MAI4, and MAI5.5, found in this system for the first time. The performed density functional theory calculations revealed the crucial role of entropy contributing to the formation of higher methylammonium polyiodides, in good agreement with experimental data. © 2019 American Chemical Society.

Petrov A.A. 1 , Fateev S.A.1 , Zubavichus Y.V. 2 , Dorovatovskii P.V. 3 , Khrustalev V.N. 4, 5 , Zvereva I.A. 6 , Petrov A.V.6 , Goodilin E.A.1, 7 , Tarasov A.B.1, 7
American Chemical Society
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  • 1 Laboratory of New Materials for Solar Energetics, Department of Materials Science, Lomonosov Moscow State University, 1 Lenin Hills, Moscow, 119991, Russian Federation
  • 2 Federal Research Center, Boreskov Institute of Catalysis, Lavrentiev Ave. 5, Novosibirsk, 630090, Russian Federation
  • 3 National Research Centre, Kurchatov Institute, 1 Acad. Kurchatov Sq., Moscow, 123182, Russian Federation
  • 4 Inorganic Chemistry Department, Peoples' Friendship University of Russia (RUDN University), 6 Miklukho-Maklay Str., Moscow, 117198, Russian Federation
  • 5 N.D. Zelinsky Institute of Organic Chemistry RAS, 47 Leninsky Prosp., Moscow, 119991, Russian Federation
  • 6 Institute of Chemistry, Saint-Petersburg State University, 26 Universitetskii prospect, Saint-Petersburg, 198504, Russian Federation
  • 7 Department of Chemistry, Lomonosov Moscow State University, 1 Lenin Hills, Moscow, 119991, Russian Federation
Ключевые слова
Differential scanning calorimetry; Perovskite; Phase diagrams; Single crystals; Thermoanalysis; Alkylammonium; Composition ranges; Low melting; Phase diversity; Photovoltaics; Related systems; Single crystal x-ray diffraction; Solvent free; Density functional theory
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