Halide Perovskite–Lead Chalcohalide Nanocrystal Heterostructures

Abstract

We report the synthesis of colloidal CsPbX3–Pb4S3Br2 (X = Cl, Br, I) nanocrystal heterostructures, providing an example of a sharp and atomically resolved epitaxial interface between a metal halide perovskite and a non-perovskite lattice. The CsPbBr3–Pb4S3Br2 nanocrystals are prepared by a two-step direct synthesis using preformed subnanometer CsPbBr3 clusters. Density functional theory calculations indicate the creation of a quasi-type II alignment at the heterointerface as well as the formation of localized trap states, promoting ultrafast separation of photogenerated excitons and carrier trapping, as confirmed by spectroscopic experiments. Postsynthesis reaction with either Cl– or I– ions delivers the corresponding CsPbCl3–Pb4S3Br2 and CsPbI3–Pb4S3Br2 heterostructures, thus enabling anion exchange only in the perovskite domain. An increased structural rigidity is conferred to the perovskite lattice when it is interfaced with the chalcohalide lattice. This is attested by the improved stability of the metastable γ phase (or “black” phase) of CsPbI3 in the CsPbI3–Pb4S3Br2 heterostructure.

Stable CsPbBr3 Nanoclusters Feature a Disk-like Shape and a Distorted Orthorhombic Structure

“… 22 , 31 , 32 CsPbBr 3 NCLs have been employed as single-source precursors for the synthesis of quantum-confined nanostructures (nanowires, nanoplatelets) 6 and NCs with complex geometries (i.e., CsPbBr 3 hexapods) 22 and heterostructures (i.e., CsPbBr 3 –Pb 4 S 3 Br 2 ). 23 Instead, conventional metal halide precursors (e.g., Cs-oleate and PbBr 2 or Cs-carbonate, Pb-acetate, and benzoyl bromide) 33 , 34 lead to a fast nucleation and growth of CsPbBr 3 NCs, making it extremely difficult to perform any seeded growth approach or to synthesize heterostructures. 35 …”

The making of a reconfigurable semiconductor with a soft ionic lattice

“…(F)High-resolution HAADF-STEM image of a single CsPbBr3-Pb4S3Br2 heterostructure with a clear interface. 75 Copyright 2021 American Chemical Society.…”

“…Even though there has been a growing number of reports on the heterogeneous, core/shell structures of halide perovskites, an atomically defined, epitaxially grown core/shell interface between halide perovskite and another covalent semiconductor has not been realized. [75][76][77] The core/shell geometry, compared with other hetero-structures such as the Janus geometry, has the advantage of protecting the halide perovskite from the attack of polar solvents or humid environments. Resolving the atomic structure of the interface is key to proving whether the heterogeneous interface is coherent or not and demonstrating how interfacial defects, such as dis-locations, are distributed (Figures 4E and 4F).…”

“…Resolving the atomic structure of the interface is key to proving whether the heterogeneous interface is coherent or not and demonstrating how interfacial defects, such as dis-locations, are distributed (Figures 4E and 4F). 75 The high crystallinity of the shell ma-terials, rather than porous or random deposition of the shell materials, is also essential for compact protection from the environment. Selection of a suitable shell material to modulate or improve the electronic properties of the core material is another consideration so that the shelling of halide perovskites will not compromise their excellent optical efficiency.…”

Simultaneous Synthesis, Modification, and DFT Calculation of Three‐Color Lead Halide Perovskite Phosphors for Improving Stability and Luminous Efficiency of WLEDs

“…In recent years, the metal halide perovskite with the general formula ABX 3 has become one of the most promising materials for solution-processable LED technology due to its high absorption coefficient, adjustable bandgap energy, and high photoluminescence quantum yield (PLQY). [17][18][19][20][21] Among them, the all-inorganic metal halide perovskite CsPbX 3 (X = Cl, Br, I) can be used as a green light-emitting element in WLED to improve the device performance due to its high color purity, high defect tolerance, and bright PL emission. [22][23][24][25][26] However, it is well known that CsPbBr 3 is prone to deterioration and it has poor thermal stability when exposed to the air for a long time.…”