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

In this work, four kinds of two-dimensional single-layered F-substituted ethylammonium lead halide perovskites (LHPs, (FxCH3-xCH2NH3)(2)PbBr4, x = 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)(2) PbBr4 shows the smallest bandgap (similar to 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)(2)PbBr4. Benefiting from the hydrophobic nature of F-C bonds, (CF3CH2NH3)(2)PbBr4 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.