Data for Picoperovskites : the smallest conceivable isolated halide perovskite structures formed within carbon nanotubes

We report four isolated sub-nm, or pico-scale, halide perovskite structures formed inside ~1.2-1.6 nm single walled carbon nanotubes (SWCNTs) by melt insertion from CsPbBr3 and lead-free CsSnI3. Three directly relate to the ABX3 perovskite archetype while a fourth is a perovskite-like lamellar structure with alternating Cs4 and polyhedral Sn4Ix layers.

In ~1.4 nm diameter SWCNTs, CsPbBr3 forms Cs3PbIIBr5 nanowires one ABX3 unit cell in cross section with the Pb2+ oxidation state maintained by ordered Cs+ vacancies. Within ~1.2 nm diameter SWCNTs, CsPbBr3 and CsSnI3 form inorganic polymer-like bilayer structures 1/4 an ABX3 unit cell in cross-section with systematically reproduced ABX3 stoichiometry. Producing these smallest halide perovskite structures at their absolute synthetic cross-sectional limit enables quantum confinement effects with first-principles calculations demonstrating band gap widening compared to corresponding bulk structural forms.