Solvent Polarity: How Does This Influence the Precursor Activation, Reaction Rate, Crystal Growth, and Doping in Perovskite Nanocrystals?

A minute difference in solvent polarity of hydrophobic solvents can drastically alter the rate of formation of cesium lead halide perovskite nanocrystals. This has been observed at room temperature and in single-solvent synthesis routes for cesium lead bromide and cesium lead chloride nanocrystals. Through the exploration Pb-thiolate as the active precursor and using seven different hydrophobic solvents, the polarity of which varied from chloroform to hexane, the phase of cesium lead bromide changed from orthorhombic-CsPbBr3 to trigonal-Cs4PbBr6. In contrast, for cesium lead chloride, the phase remained cubic-CsPbCl3 in all solvents, but their shape turned from cube to platelet. Because the rate of the reaction was controlled here, doping of Mn(II) was performed for all cases, and efficient doping was observed for the slower reaction in the hexane medium. The reaction chemistry and the physical processes associated with these formation processes were systematically analyzed and are reported in this Letter.