Ligand Mediated Transformation of Cesium Lead Bromide Perovskite Nanocrystals to Lead Depleted Cs₄PbBr₆ Nanocrystals

Abstract

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.

Photoelectrochemically Active and Environmentally Stable CsPbBr3/TiO2 Core/Shell Nanocrystals

“…[1a,9c,10] Moreover, there is no efficient way to fabricate a semiconductor shell to form exquisite core/shell structures with uniform morphology, with respect to traditional II−VI, III−V, and IV−VI semiconductor NCs, [12] because of the ionic nature and fast anion exchange of lead halide perovskites. [13] Thus, it is imperative to develop new strategies for water-stable perovskite NCs while maintaining good charge transport properties for optoelectronic and related applications.…”

Zero-Dimensional Cesium Lead Halides: History, Properties, and Challenges

“…These Cs 4 PbX 6 NCs are spherical or hexagonally shaped for small NCs (<20 nm) and often rhombohedral for larger NCs, which strongly differs from the highly cubic CsPbX 3 NCs, and strongly reflects their hexagonal crystal structure. 13,33,37 Interestingly, these NCs are often synthesized under similar conditions to those of the highly luminescent CsPbBr 3 NCs, but they use a higher amount of alkylamine. Here, the nucleation of CsPbBr 3 can be completely suppressed because oleylamine strongly binds to Pb 2+ .…”

“…13,27 This can be done via the insertion of PbBr 2 , the extraction of CsBr with water or with Prussian Blue, or the extraction of Pb 2+ with amines. 13,27,28,33,37 Several groups have reported that the size and shape of the starting Cs 4 PbBr 6 NCs can be used to tune the size of the final CsPbBr 3 NCs (Figure 5b). 13,27,28,33,37 The transformed CsPbBr 3 NCs exhibit a strong green PL, similar to the PL of directly synthesized CsPbBr 3 NCs, and they show no excitonic absorption in the UV from their parent Cs 4 PbBr 6 NCs (Figure 5c).…”

Strategy to overcome recombination limited photocurrent generation in CsPbX3 nanocrystal arrays

“…In particular, these materials present some stability issues: PNCs degrade under an electron beam 15 and undergo structural phase changes or ligand-induced stoichiometry change. 16 As a result, PNCs need to be handled with great care and the conventional method to build conductive nanocrystal-based films need to be revised. For example, a phase transfer ligand exchange toward S 2-capping, although quite successful for metal chalcogenide nanocrystals, 17,18 cannot be applied to PNCs.…”