Nucleation, growth and structural transformations of perovskite nanocrystals
Dan Oron a, Miri Kazes a, Thumu Udayabhaskararao a, Lothar Houben b, Hong Lin c
a Tsinghua University, Yifu Building Room 2422, Tsinghua University,Haidian District, Beijing, 100084, China
Proceedings of Perovskite Thin Film Photovoltaics (ABXPV17)
València, Spain, 2017 March 1st - 2nd
Organizers: Henk Bolink and David Cahen
Oral, presentation 062
Publication date: 18th December 2016

The outstanding efficiencies of organic-inorganic perovskite thin film based solar cells led to interest in increasing the range of perovskite materials. One such family of materials is the all inorganic CsPbX3 colloidal nanocrystals (NCs). Despite the recent surge of synthetic protocols producing different shapes and crystal structures, there are still significant gaps in the understanding of nucleation and growth processes involved in their formation. Here we try to address the mechanisms and the common factors behind these multiple synthetic pathways.We have identified that the formation of CsPbX3 NCs follows through two separate stages. First, seed mediated nucleation through the formation of metal Pb NCs. Second, further growth is attained through oriented attachment. We were able to investigate the two stages independently by significantly slowing down the kinetics and by the separate successive additions of ligands. It was found that the critical factor determining the size, shape and crystallographic structure of the CsPbX3 NCs is the polarity of the ligands. Using this understanding we could synthesize other novel materials such as CsPbBr3 nanowires, CsPbCl3 bulk-like crystals and CsPbI3 orthorhombic nanowires of length ranging from 200 nm to several microns.We believe this work will lead to the development of improved strategies for rational design of synthesis and more importantly, the stabilization of perovskite NCs which may offer an advantage for perovskite NCs over thin films for photovoltaics and other potential applications.

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