Short Aromatic Diammonium Ions Modulate Distortions in 2D Lead Bromide Perovskites for Tunable White-Light Emission
Résumé
White-light broadband emission in the visible range from the low-dimensional halide perovskites is commonly attributed to structural distortions in lead bromide octahedra. In this paper, we report Dion−Jacobson-phase two-dimensional (2D) lead bromide perovskites based on short aromatic diammonium cations, p-phenylene diammonium (pPDA), m-phenylene diammonium (mPDA), and two 1D compounds templated by o-phenylene diammonium (oPDA). All of the compounds exhibit white-light emission. Single-crystal X-ray diffraction analysis reveals that the distortion of the Pb octahedra is influenced by the stereochemistry of the cations and their interactions with the perovskite layers. Solid state 1 H and 207 Pb NMR spectroscopy analysis further confirms this trend, whereby different 1 H and 207 Pb chemical shifts are observed for the pPDA and mPDA spacer cations, indicating different hydrogenbonding interactions and octahedral distortions. Owing to the octahedral distortion, 2D (mPDA)PbBr4 compounds exhibit broader white-light emission than 2D (pPDA)PbBr4. Density functional theory calculations suggest that (pPDA)PbBr4 and (mPDA)PbBr4 are direct-band-gap semiconductors, and they exhibit larger electronic band gaps and effective masses than the Ruddlesden−Popper-phase (BA)2PbBr4. Among the films of these compounds, 2D (mPDA)PbBr4 shows the best stability, which is attributed to stronger hydrogen-bonding interactions in the material.
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