title: How Lead Halide Complex Chemistry Dictates the Composition of Mixed Halide Perovskites.
abstract: Varying the halide ratio (e.g., Br(-):I(-)) is a convenient approach to tune the bandgap of organic lead halide perovskites. The complexation between Pb(2+) and halide ions is the primary step in dictating the overall composition, and optical properties of the annealed perovskite structure. The complexation between Pb(2+) and Br(-) is nearly 7 times greater than the complexation between Pb(2+) and I(-), thus making Br(-) a dominant binding species in mixed halide systems. Emission and transient absorption measurements show a strong dependence of excited state behavior on the composition of halide ions employed in the precursor solution. When excess halide (X = Br(-) and I(-)) are present in the precursor solution (0.3 M PbX2 and 0.9 M CH3NH3X), the exclusive binding of Pb(2+) with Br(-) results in the formation of CH3NH3PbBr3 perovskites as opposed to mixed halide perovskite.
authors.affiliation: Radiation Laboratory, ‡Department of Chemistry and Biochemistry, and §Department of Chemical and Biomolecular Engineering, University of Notre Dame , Notre Dame, Indiana 46556, United States.
authors.forename: Seog Joon
authors.initials: SJ
authors.lastname: Yoon
authors.affiliation: Radiation Laboratory, ‡Department of Chemistry and Biochemistry, and §Department of Chemical and Biomolecular Engineering, University of Notre Dame , Notre Dame, Indiana 46556, United States.
authors.forename: Kevin G
authors.initials: KG
authors.lastname: Stamplecoskie
authors.affiliation: Radiation Laboratory, ‡Department of Chemistry and Biochemistry, and §Department of Chemical and Biomolecular Engineering, University of Notre Dame , Notre Dame, Indiana 46556, United States.
authors.forename: Prashant V
authors.initials: PV
authors.lastname: Kamat