Picoperovskites: the smallest conceivable isolated halide perovskite structures formed within carbon nanotubes
This work*, published in Advanced Materials, describes the synthesis and characterization of 'picoperovskites' - tiny wire-like objects derived from the halide perovskites (a class of materials under intense investigation due to their potential functional applications, particularly in photovoltaics).
Experimental researchers at the University of Warwick and SuperSTEM have successfully taken two typical inorganic halide perovskites - CsSnI3 and CsPbBr3 - encapsulated them within carbon nanotubes, and then imaged the results. In order to interpret the electron microscopy images, the computational modelling was carried out in Oxford Materials' MML. Four different structures were identified, including a remarkable Cs-Pb-Br structure which is just one CsPbBr3 'unit' wide (see image, left) and a Cs-Sn-I structure with no bulk analogue, consisting of Cs layers interspersed with mixed Sn-I layers.
The electronic structure calculations provide a striking demonstration of quantum confinement, with the band gap of the perovskites opening by approximately 2eV when they are confined inside the nanotube. The calculations also emphasise the connection between structural stability and nanotube diameter, such that improved control of the latter should allow preferential growth of particular structures.
