Anisotropic colloidal quasi-two-dimensional
nanoplates (NPLs) hold
great promise as functional materials due to their combination of
low dimensional optoelectronic properties and versatility through
colloidal synthesis. Recently, lead-halide perovskites have emerged
as important optoelectronic materials with excellent efficiencies
in photovoltaic and light-emitting applications. Here we report the
synthesis of quantum confined all inorganic cesium lead halide nanoplates
in the perovskite crystal structure that are also highly luminescent
(PLQY 84%). The controllable self-assembly of nanoplates either into
stacked columnar phases or crystallographic-oriented thin-sheet structures
is demonstrated. The broad accessible emission range, high native
quantum yields, and ease of self-assembly make perovskite NPLs an
ideal platform for fundamental optoelectronic studies and the investigation
of future devices.
Lead halide perovskite nanocrystals (NCs) have emerged as attractive nanomaterials owing to their excellent optical and optoelectronic properties. Their intrinsic instability and soft nature enable a post-synthetic controlled chemical transformation. We studied a ligand mediated transformation of presynthesized CsPbBr NCs to a new type of lead-halide depleted perovskite derivative nanocrystal, namely CsPbBr. The transformation is initiated by amine addition, and the use of alkyl-thiol ligands greatly improves the size uniformity and chemical stability of the derived NCs. The thermodynamically driven transformation is governed by a two-step dissolution-recrystallization mechanism, which is monitored optically. Our results not only shed light on a decomposition pathway of CsPbBr NCs but also present a method to synthesize uniform colloidal CsPbBr NCs, which may actually be a common product of perovskite NCs degradation.
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