Tailoring CsPbBr Growth Non-Polar Solvent Choice and Heating Methods.

This study describes an investigation of the role of non-polar solvents on the growth of cesium lead halide (CsPbX X = Br and I) nanoplatelets. We employed two solvents, benzyl ether (BE) and 1-octadecene (ODE), as well as two nucleation and growth mechanisms, one-pot, facilitated by microwave irradiation (MWI)-based heating, and hot-injection, using convection. Using BE and MWI, large mesoscale CsPbBr nanoplatelets were produced, whereas use of ODE produced small crystallites. Differences between the products were observed by optical spectroscopies, which showed first band edge absorptions consistent with thicknesses of ∼9 nm [∼15 monolayer (ML)] for the BE-CsPbBr and ∼5 nm (∼9 ML) for ODE-CsPbBr. Both products had orthorhombic crystal structures, with the BE-CsPbBr revealing significant preferred orientation diffraction signals consistent with the asymmetric and two-dimensional platelet morphology. The differences in the final morphology were also observed for products formed hot injection, with BE-CsPbBr showing thinner square platelets with thicknesses of ∼2 ML and ODE-CsPbBr showing similar morphologies and small crystallite sizes. To understand the role solvent plays in crystal growth, we studied lead plumbate precursor (PbBr) formation in both solvents, as well as solvent plus ligand solutions. The findings suggest that BE dissolves PbBr salts to a higher degree than ODE, and that this BE to precursor affinity persists during growth.