Investigation on broadband emission of two-dimensional melamine lead iodide perovskite (2D-C3H8N6PbI4): An experimental and theoretical approach.

[Display omitted] • Broadband emission of 2D-C 3 H 8 N 6 PbI 4 and comparisons with 2D-C 3 H 8 N 6 PbCl 4 and 2D-C 3 H 8 N 6 PbBr 4. • Experimental and theoretical support for energy transfer resulted broadband emission. • Crystallinity and lattice distortion of 2D-C 3 H 8 N 6 PbI 4 are confirmed from XRD studies. • Optical band gaps of 2D-C 3 H 8 N 6 PbX 4 (X = Cl, Br, and I) are verified by DFT. • Gaussian fitting of PL spectra clarify the broadband emission in 2D-C 3 H 8 N 6 PbX 4 (X = Cl, Br, and I). Novel two-dimensional melamine lead iodide perovskite (2D-C 3 H 8 N 6 PbI 4) is synthesized to investigate its crystallinity, optical band gap and broadband emission properties and to make comparisons with 2D-C 3 H 8 N 6 PbCl 4 /2D-C 3 H 8 N 6 PbBr 4 perovskites. Both experimental and density functional theory (DFT) interrogations on 2D-C 3 H 8 N 6 PbX 4 (X = Cl, Br and I) are conducted. The crystal structure, morphology and percentile of Pb and halide elements are confirmed using scanning electron microscope (SEM), and energy dispersive spectrum (EDS), powder/single crystal X-ray diffraction (PXRD/SXRD), DFT and X-ray crystallography simulations. The optical band gaps of 2D-C 3 H 8 N 6 PbX 4 perovskites are determined from the Tauc plot fitting of absorbance and DFT studies. Distinct broadband emission of 2D-C 3 H 8 N 6 PbX 4 perovskites between 300 and 800 nm is observed, which can be fitted with multiple Gaussian distributions. The fittings of broad PL spectra from 2D-C 3 H 8 N 6 PbCl 4 /2D-C 3 H 8 N 6 PbBr 4 perovskites confirm the involvement of both Dexter energy transfer from melamine cation and self-trapped excitons (STEs). However, the broadband emission of 2D-C 3 H 8 N 6 PbI 4 is attributed only to the Dexter energy transfer from melamine cation and the absence of STEs is attributed to the larger lattice deformation of 2D-C 3 H 8 N 6 PbI 4. Moreover, the involvement of spin–orbit coupling (SOC) in the energy transfer is clarified to attest that the broadband emission of 2D-C 3 H 8 N 6 PbI 4 is distinct among its halide family. [ABSTRACT FROM AUTHOR]