Top-Down Fabrication of Stable Methylammonium Lead Halide Perovskite Nanocrystals by Employing a Mixture of Ligands as Coordinating Solvents

A top-down method is demonstrated for the fabrication of CH₃NH₃PbBr₃ and CH₃NH₃PbI₃ perovskite nanocrystals, employing a mixture of ligands oleic acid and oleylamine as coordinating solvents. This approach avoids the use of any polar solvents, skips multiple reaction steps by employing a simple ultrasonic treatment of the perovskite precursors, and yields rather monodisperse blue-, green-, and red-emitting methylammonium lead halide nanocrystals with a high photoluminescence quantum yield (up to 72 % for the green-emitting nanocrystals) and remarkably improved stability. After discussing all relevant reaction parameters, the green-emitting CH₃NH₃PbBr₃ nanocrystals are employed as a component of down-conversion white-light-emitting devices_.