Broadband Photoluminescence in 2D Organic–Inorganic Hybrid Perovskites: (C7H18N2)PbBr4 and (C9H22N2)PbBr4

Organic–inorganic hybrid perovskites have aroused intense research interest because of their excellent physical performance and potential for use in optoelectronic field. Herein, we report two new 2D hybrid lead bromides, (C7H18N2)PbBr4 [C7H18N2 is 1,7-diaminoheptane] and (C9H22N2)PbBr4 [C9H22N2 is 1,9-diaminononane], both of which possess ⟨100⟩-oriented inorganic layers consisting of corner-sharing octahedra. The optical bandgaps are experimentally determined to be 2.76 eV for (C7H18N2)PbBr4 and 2.78 eV for (C9H22N2)PbBr4. Upon 390 nm excitation, (C7H18N2)PbBr4 exhibits white-light emission centered at 600 nm, and (C9H22N2)PbBr4 exhibits red-light emission centered at 620 nm. These broad photoluminescent spectra originate from the synergistic emission of free excitons (FEs) and self-trapped excitons (STEs). This work provides a strategy for realizing single-component white-light emission and efficient red-light emission in two-dimensional perovskites, demonstrating the vast application prospects of 2D perovskites in photoelectric devices.