Fig. 4: Mechanisms of narrow-band emission.
From: Suppressing electron–phonon coupling for narrow-band emitting Eu(II)-based perovskitoids
a The number of crystallographically distinct Eu(II) sites dependent full width at half maximum (FWHM) for narrow-band cyan Eu(II)-based perovskitoids. b The distortion index (Δd) and the bond angle variance (σ2) of polyhedral distortion in TEtEuBr3. c Huang–Rhys factor (S), FWHM and electrostatic potential (ESP). d The one-dimensional configurational coordinate model of TEtEuBr3 with ground state (A, D dots) and excited state (B, C dots). e The coordinate position change of each atom in TEtEuBr3 at the excited state relative to the ground state. f The bond length change of Eu-Br in TEtEuBr3 at the excited state (ES-C dot) relative to the ground state (GS-A dot). g Calculated vibrational density of states (DOS) (upper panel) and Raman spectrum (lower panel) in the experiment for TEtEuBr3. h The distribution map of calculated Huang–Rhys factor. i Calculated emission spectrum compared with the experimental result. The calculated curve was shifted to align its maximum with that of the experimental emission spectrum for better comparison.
