Tailoring CsPbBr3 Growth Via Non-Polar Solvent Choice and Heating Method

This study describes an investigation of the role of non-polar solvents on the growth of cesium lead halide (CsPbX3 X = Br, 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 conventional heating. Using BE and MWI, large mesoscale CsPbBr3 nanoplatelets were produced, whereas use of ODE produced thin 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-CsPbBr3, and ~5 nm (~9 ML) for ODE-CsPbBr3. Both products had orthorhombic crystal structure, with the BE-CsPbBr3 revealing significant preferred orientation diffraction signals consistent with the asymmetric and two-dimensional (2D) platelet morphology. The differences in final morphology were also observed for products formed via hot-injection, with BE-CsPbBr3 showing thinner square platelets with thicknesses of ~2 ML, and ODE-CsPbBr3 showing similar morphologies and small crystallite sizes. To understand the role solvent plays in crystal growth, we studied lead plumbate precursor (PbBrn2-n) formation in both solvents, as well as solvent plus ligand solutions. The findings suggest that BE dissolves PbBr2 salts to a higher degree than ODE, and that this BE to precursor affinity persists during growth.