Fluorinated Spacers Regulate the Emission and Bandgap of Two-Dimensional Single-Layered Lead Bromide Perovskites by Hydrogen Bonding

Abstract

In this work, four kinds of two-dimensional single-layered F-substituted ethylammonium lead halide perovskites (LHPs, (F_<i>x</i>CH_3-<i>x</i>CH₂NH₃)₂PbBr₄, <i>x</i> = 0, 1, 2, and 3) are successfully synthesized. The introduction of terminal F atoms promotes the formation of an inter- and intramolecular hydrogen bonding network, which has a great impact on the configuration of F-substituted EA, the interlayer spacing, and distortion of inorganic layers. Among these four as-prepared samples, (FCH₂CH₂NH₃)₂PbBr₄ shows the smallest bandgap (∼2.72 eV) and best photoconductivity because of the interlayer electronic coupling. Owing to the strong coupling between excitons and lattice, intense white light emission (quantum yield: 12%) is observed for (F₂CHCH₂NH₃)₂PbBr₄. Benefiting from the hydrophobic nature of F-C bonds, (CF₃CH₂NH₃)₂PbBr₄ presents a greatly improved stability toward moisture. These findings reveal that constructing inter- and intramolecular interaction can serve as an effective approach for tuning the broadband emission and the interlayer conductivity of single-layered LHPs.