(INVITED) Understanding Solvent-Precursor Interactions and Reactions in Halide Perovskite Solutions

Conference · Wed Dec 04 04:00:00 EST 2019

DOI:https://doi.org/10.2172/1659405· OSTI ID:1659405

Loo, Lynn ^[1]

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1. Princeton University

Hybrid organic-inorganic perovskites (HOIPs) formed from organoammonium iodide and lead iodide precursor solutions are promising materials for photovoltaic applications. While lead polyiodide and lead-solvent complexes formed in solution are intermediates for HOIP crystallization, the influence of solvent choice upon the formation of such intermediates is not well understood. In this talk, I will highlight two examples in which solution chemistries can drastically impact solid-state structural development, and consequently, performance of solar cells that incorporate these films. In the first example, I will show how the formation of lead polyiodides in the precursor solutions is correlated with the basicity of the processing solvent (quantified by Gutmann’s donor number, DN). Solvents with low DN exhibit a strong propensity to form lead polyhalides. We infer that such solvents interact weakly with the lead salt precursor. These solvents favor the precipitation of HOIP single crystals from solution. Conversely, high-DNsolvents suppress the formation of lead polyiodides, indicative of strong lead-solvent coordination. Such solvents support the formation of stable precursor solutions for HOIP thin-film processing and may be added in fractional quantities to tune the basicity of the processing solvent. The tunability introduced by high-DNadditives provides finer control over perovskite crystallization, post-deposition processability, and the morphology of HOIP active layers for photovoltaic applications. In the second example, I will highlight undesirable side reactions that take place between DMSO, a common Lewis base additive for perovskite processing, with perovskite precursors. We identified two distinct reaction pathways by which dimethylammonium and ammonium are produced as a result of reactions between DMSO and methyammonium cation; contrary to previous reports in the literature, these reactions need not be catalyzed by the presence of formic acid. The presence of these impurities alter the stoichiometry of the precursor solution, and when incorporated in the solid state alters the perovskite structure and optoelectronic properties.

• Research Organization: Princeton University
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
• DOE Contract Number: EE0008560
• OSTI ID: 1659405
• Country of Publication: United States
• Language: English