Role of Octahedron Alloying in Photodynamics of Lead‐Free Halide Double Perovskite Nanoplatelets

Abstract

The lead‐free halide double perovskites have attracted great interest owing to their unique photophysical properties. Among them, the luminescence mechanisms of the Cs2AgInCl6 crystallites are still under debate. A hot‐injection method is developed to synthesize novel hollow and spatially symmetric Cs2AgInCl6 nanoplatelets (NPLs) and study the effect of the cation/octahedron alloying on their photodynamics by using the experimental characterizations in conjunction with the density functional theory calculations. The results reveal that the pure Cs2AgInCl6 NPLs exhibit wide‐band and double‐peaked photoluminescence originating separately from free and self‐trapped excitons. The Ag+/Na+ and In3+/Bi3+ alloying, that is, the partial substitution of the [AgCl6]5− and [InCl6]3− octahedra by [NaCl6]5− and [BiCl6]3− octahedra, leads to crystal symmetry breaking and strongly enhanced exciton localization. As a result, the self‐trapped exciton luminescence becomes predominant in the yielded Cs2AgInCl6:NaBi nanoplatelets, and the quantum yield is highly improved to 10.8%. These results improve the understanding of the role of octahedron alloying in the photophysics of the double perovskite nanocrystals and pave the way for their applications in solid‐state lighting.

Transformations of 2D to 3D Double-Perovskite Nanoplates of Cs2AgBiBr6 Composition

“…The imperfection often possesses right angle missing pieces, which we assign to a defective assembly and fusing process of smaller nanoplates (see Figure S15). This is in line with previous studies of self-assembled nanoplate systems. ,, …”

“…This is in line with previous studies of self-assembled nanoplate systems. 24,27,50 ■ CONCLUSIONS In summary, we further study the formation of doubleperovskite Cs 2 AgBiBr 6 nanosheets. The building blocks of the nanosheets are based on advances in the colloidal synthesis of two-dimensional layered perovskites.…”

Broadband Emission Origin in Metal Halide Perovskites: Are Self‐Trapped Excitons or Ions?

“…[105][106][107][108][109] Through the continuous efforts, various low-dimensional perovskites have been developed, and the PLQY has been increased to over 90% in the low-dimensional metal halides perovskites. [18,26,57,59] In the low-dimensional perovskites system, their electron-phonon coupling and the structural distortion is well controlled by intentional non-ns 2 -ions doping; [110][111][112] designing suitable organic ammonium cations, [57,68,103,104] and employing external pressure compression. [68,[113][114][115] As to the lowdimensional perovskites, the bulky organic layers and inorganic layers are alternately and periodically arranged.…”

Facet-Defect Tolerant Bi-Doped Cs2AgxNa1–xInCl6 Nanoplatelets with a Near-Unity Photoluminescence Quantum Yield

“…Liu et al further pushed the QY of the nanocrystals to 68% by making sure that no Ag 0 species formed during the synthesis and by partial alloying at the B + site with K + ions (by a few percent), which slightly increased the lattice parameter and ensured a higher density of surface ligands . Morphology control appears to be another way to improve the optical properties of double perovskites at the nanoscale. − Although Ma et al reported a PLQY of only 11% from Cs 2 AgInCl 6 :NaBi nanoplatelets (NPLs), , in another work Liu et al synthesized Cs 2 AgIn x Bi 1– x Cl 6 NPLs with a PLQY of 40%, much higher than that of the corresponding Bi-doped Cs 2 AgInCl 6 nanocubes (∼11%) . These promising results suggest that tuning the nanocrystal shape may represent a convenient way to optimize the PLQY.…”