A new metric to control nucleation and grain size distribution in hybrid organic-inorganic perovskites by tuning the dielectric constant of the antisolvent

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2021-02, Vol.9 (6), p.3668-3676
• Main Authors: Sorenson, Blaire A, Yoon, Lucy U, Holmgren, Eric, Choi, Joshua J, Clancy, Paulette
• Format: Article
• Language: English
• Subjects: Cations; Complexation; Computer applications; Density functional theory; Dielectric constant; Dielectric strength; Grain size; Grain size distribution; Iodides; Lead; Lead isotopes; Magnetic spectroscopy; New species; Nucleation; Particle size; Perovskites; Precursors; Scanning electron microscopy; Size distribution; Solvent extraction; Solvents; Spectroscopy; Spectrum analysis; Thin films
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d0ta12364a

In perovskite research, there is a widely exploited but poorly explained phenomenon in which the addition of "antisolvents (ATS)" to precursor solutions results in higher-quality films. We explain the mechanism and driving force underlying an antisolvent-driven solvent extraction process. Density functional theory calculations uncover the defining effects of antisolvent choice on the extent of complexation between a lead salt and a methylammonium cation in solution. We experimentally validate the computational results using ultraviolet-visible spectroscopy and 207 Pb nuclear magnetic spectroscopy of methylammonium lead iodide solutions, containing both a processing solvent and an antisolvent. Furthermore, we uncover, and subsequently identify, the appearance of new species in solution as a result of the addition of the antisolvent. We observe that the choice of antisolvent has a substantial effect on the nature of the complexation of the methylammonium lead iodide (MAPbI 3 ) precursor species, whose origin we explain at an atomic level; specifically, the lower the dielectric of the antisolvent, the stronger the intermolecular binding energy between methylammonium cation (MA + ) cation and PbI 3 − plumbate, independent of the solvent or antisolvent interaction with the lead salt. Thin films were characterized using scanning electron microscopy; images of the films show how the addition of an antisolvent influences and, importantly, can be used to alter thin-film grain size. Grain size and distribution in thin films is reflected by the choice of antisolvent, promoting slower nucleation rates, a lower nucleation density, and hence larger final grain size. In perovskite research, there is a widely exploited but poorly explained phenomenon in which the addition of "antisolvents (ATS)" to precursor solutions results in higher-quality films.