Fig. 1. Spectral characteristics of (BA)₂BI₄ (B: Sn/Pb) perovskites. (a) Schematic of the hybrid quantum-well structure of the crystal structure, showing the perovskite octahedra sandwiched between organic spacer molecules (BA⁺). The UV-visible (UV-Vis) absorption, steady-state photoluminescence (PL) spectra of (b) (BA)₂SnI₄ and (c) (BA)₂PbI₄. (d) PLQY of (BA)₂SnI₄ and (BA)₂PbI₄.

Fig. 2. Analysis of PL characteristics. (a) Multi-peak fit analysis of (BA)₂PbI₄, (b) multi-peak fit analysis of (BA)₂SnI₄, (c) percentage of subpeaks of (BA)₂PbI₄ and (BA)₂SnI₄, (d) normalized PL decay kinetics.

Fig. 3. Temperature dependence of the steady-state PL spectra. Contour map of the temperature-dependent steady-state PL spectra of (a) (BA)₂SnI₄ and (b) (BA)₂PbI₄. Fitting of the temperature-dependent FWHM of (c) (BA)₂SnI₄ and (d) (BA)₂PbI₄. The red fitting line of the data (blue point) is obtained by Eq. (1).

Fig. 4. Carrier relaxation dynamics. False-color 2D TA mappings of (a) (BA)₂SnI₄ and (b) (BA)₂PbI₄. Evolution-associated spectra (EAS) obtained upon global analysis of the TA data of (c) (BA)₂SnI₄ and (d) (BA)₂PbI₄. Decay-associated spectra (DAS) obtained by performing global analysis on the TA spectra of (e) (BA)₂SnI₄ and (f) (BA)₂PbI₄. The inset shows the results of fitting the band-edge exciton relaxation dynamics.

Table 1. Best-Fitting Parameters of the (BA)₂SnI₄ and (BA)₂PbI₄ Perovskites