Bismuth-Based Halide Double Perovskite Cs₂LiBiCl₆: Crystal Structure, Luminescence, and Stability

Abstract

A new bismuth-based halide double perovskite Cs2LiBiCl6 was isolated successfully using solid-state reactions. The crystal structure was investigated using X-ray diffraction and complemented by 7Li solid-state nuclear magnetic resonance spectroscopy, which indicated the highly ordered nature of Li and Bi ions in the B sublattice of double perovskite. Compared with the Na analogue, the more moisture-sensitive Cs2LiBiCl6 has a smaller indirect band gap of 3.15(2) eV and red-shift luminescence of around 612 nm as well as stronger intensities at Mn2+ doping. The stability mechanism of Cs2LiBiCl6 was discussed together with that of Cs2NaBiCl6 and their inaccessible Br counterparts based on the tolerance and octahedral factors and density functional theory (DFT) calculations. Owing to the small size of Li+ cations, Cs2LiBiCl6 has low tolerance and octahedral factors close to the boundary between the stable perovskite and nonperovskite compounds, which possess a small decomposition energy and thus easily coexist with other ternary phases. The Br-based compositions of Cs2LiBiBr6 and Cs2NaBiBr6 have even smaller octahedral factors and negative decomposition energies, and therefore their double perovskite polymorphs are destabilized. DFT simulations indicate that the moisture sensitivity of Cs2LiBiCl6 is related to the coordination preference of Li+ due to its smaller size and the steric effect from water molecules, in contrast with the larger Na+ showing a more stable octahedral configuration under the water incorporation. These mechanisms combining the geometry factors and decomposition energies provide new insights into the stability of halide double perovskites.

Multiple Anion Chemistry for Ionic Layer Thickness Tailoring in Bi2+2nO2+2nSenX2 (X = Cl, Br) van der Waals Semiconductors with Low Thermal Conductivities

“…The absorption tail at ∼1250 nm for Bi 4 O 4 SeBr 2 and Bi 4 O 4 SeCl 2 can be attributed to the extrinsic defect states. Given that the Bi 2 O 2 Se and Bi 2 O 2 Cl 2 (Bi 2 O 2 Br 2 ) end-member materials have indirect band gaps of ∼0.8 and 3.46 eV (2.92 eV), respectively, ,, the intergrowth materials Bi 4 O 4 SeX 2 and Bi 6 O 6 Se 2 X 2 most probably have indirect band gaps, which could be obtained on the Tauc plot as the intercept on the dashed baseline from the linear fits to the [ F ( R ) E ] 1/2 at the intrinsic absorption edge of 860–1000 nm. , From the corresponding Tauc plots (Figure b), the indirect band gaps of Bi 4 O 4 SeBr 2 , Bi 4 O 4 SeCl 2 , and Bi 6 O 6 Se 2 Cl 2 were estimated to be 1.07(5), 1.05(5), and 1.04(5) eV, respectively, with the value for Bi 4 O 4 SeCl 2 matching well with the reported value of 1.15(5) eV . An extrinsic defect-related sub-bandgap was estimated to be 0.73(5) and 0.75(5) eV for Bi 4 O 4 SeBr 2 and Bi 4 O 4 SeCl 2 , respectively (Figure b).…”

Trap-tuning in afterglow perovskite crystals through alkali metal ion doping

“…The Mn-doped crystal showed a red emission centering at 623 nm, which was attributed to 4 T 1 → 6 A 1 transition emission of octahedrally coordinated Mn 2+ . 18 The PLE peak is located at 351 nm, featuring a typical transition of In 5s 2 ( 1 S 0 → 3 P 1 ). 19 Intriguingly, both the PLE and PL peaks remained unchanged after heavy-doping of alkali metal ions, which could be explained by the localized nature of both ionic transitions (Fig.…”

Phase-Selective Solution Synthesis of Cd-Based Perovskite Derivatives and Their Structure/Emission Modulation

“…The chemical formula of these derivatives can be described as A 2 B IV X 6 , A 3 B III 2 X 9 , AB III X 4 , or A 2 B II X 4 , etc. − Another approach is to replace two Pb 2+ ions with two different aliovalent ions to form double perovskites (DPs) with the chemical formula A 2 B I B III X 6 (where B I = Li + , Na + , K + and B III = In 3+ , Sb 3+ , Bi 3+ , etc. ). ,− These perovskite derivatives can be divided into three-dimensional (3D), two-dimensional (2D), one-dimensional (1D), or zero-dimensional (0D) structures on the basis of the arrangements of sublattice polyhedron. , Various structural dimensions lead to the difference in electronic structures and photophysical properties.…”