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Kinetic Molecular Cationic Control of Defect-Induced Broadband Light Emission in 2D Hybrid Lead Iodide Perovskites
preprintsubmitted on 30.10.2020, 20:25 and posted on 02.11.2020, 09:43 by Adedayo M. Sanni, Aaron Rury
In this study we examine the effects of changing organic cation concentrations on the efficiency and photophysical implications of exciton trapping in 2-dimensional hybrid lead iodide self-assembled quantum wells (SAQWs). We show increasing the concentration of alkyl and aryl ammonium cations causes the formation of SAQWs at a liquid-liquid interface to possess intense, broadband subgap photoluminescence (PL) spectra. Electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopic studies suggest materials formed under these cation concentrations possess morphologies consistent with inhibited crystallization kinetics, but exhibit qualitatively similar bulk chemical bonding to non-luminescent materials stabilized in the same structure from precursor solutions containing lower cation concentrations. Temperature and power-dependent PL spectra suggest the broadband subgap light emission stems from excitons self-trapped at defect sites, which we assign as edge-like, collective iodide vacancies using a simple model of the chemical equilibrium driving material self-assembly. These results suggest changes to the availability of molecular cations can suitably control the light emission properties of self-assembled hybrid organic-inorganic materials in ways central to their applicability in lighting technologies.