CsPbBr3 and CsPbI3 rhombic dodecahedra and nanocubes displaying facet-dependent optical properties

Abstract

CsPbBr₃ rhombic dodecahedra, octahedra, and nanocubes have been synthesized using typical reagents but by adjusting the amounts of organic capping molecules used and the reaction temperature. Although some Cs₄PbBr₆ has been identified, its presence was found not to affect optical property examination. With increasing sizes of CsPbBr₃ rhombic dodecahedra from 59 to 168 nm, their band gaps decrease gradually. Remarkably, the much larger octahedra and {110}-bound rhombic dodecahedra show more blue-shifted absorption wavelengths than the {100}-bound nanocubes do, demonstrating the presence of optical facet effects. 10 nm CsPbI₃ nanocubes were also prepared and anion-exchanged to CsPbBr₃ nanocubes. Similarly, CsPbBr₃ rhombic dodecahedra were converted to rhombic dodecahedral CsPbI₃. For both compositions, the much larger rhombic dodecahedra still display more blue-shifted absorption and emission bands than those of the nanocubes, indicating very large optical band shifts are possible by tuning the crystal morphology or exposed surfaces.