A Mechanistic Study of Phase Transformation in Perovskite Nanocrystals Driven by Ligand Passivation

Thumu Udayabhaskararao, Lothar Houben, Hagai Cohen, Matan Menahem, Iddo Pinkas, Liat Avram, Tamar Wolf, Ayelet Teitelboim, Michal Leskes, Omer Yaffe, Dan Oron, Miri Kazes

Research output: Contribution to journalArticlepeer-review

153 Scopus citations


Active control over the shape, composition, and crystalline habit of nanocrystals has long been a goal. Various methods have been shown to enable postsynthesis modification of nanoparticles, including the use of the Kirkendall effect, galvanic replacement, and cation or anion exchange, all taking advantage of enhanced solid-state diffusion on the nanoscale. In all these processes, however, alteration of the nanoparticles requires introduction of new precursor materials. Here we show that for cesium lead halide perovskite nanoparticles, a reversible structural and compositional change can be induced at room temperature solely by modification of the ligand shell composition in solution. The reversible transformation of cubic CsPbX3 nanocrystals to rhombohedral Cs4PbX6 nanocrystals is achieved by controlling the ratio of oleylamine to oleic acid capping molecules. High-resolution transmission electron microscopy investigation of Cs4PbX6 reveals the growth habit of the rhombohedral crystal structure is composed of a zero-dimensional layered network of isolated PbX6 octahedra separated by Cs cation planes. The reversible transformation between the two phases involves an exfoliation and recrystalliztion process. This scheme enables fabrication of high-purity monodispersed Cs4PbX6 nanoparticles with controlled sizes. Also, depending on the final size of the Cs4PbX6 nanoparticles as tuned by the reaction time, the back reaction yields CsPbX3 nanoplatelets with a controlled thickness. In addition, detailed surface analysis provides insight into the impact of the ligand composition on surface stabilization that, consecutively, acts as the driving force in phase and shape transformations in cesium lead halide perovskites.

Original languageEnglish
Pages (from-to)84-93
Number of pages10
JournalChemistry of Materials
Issue number1
StatePublished - 9 Jan 2018
Externally publishedYes

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© 2017 American Chemical Society.


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