Stable and Size Tunable CsPbBr<sub>3</sub> Nanocrystals Synthesized with Oleylphosphonic Acid
Baowei Zhang, Luca Goldoni, Chiara Lambruschini, Lisa Moni, Muhammad Imran, Andrea Pianetti, Valerio Pinchetti, Sergio Brovelli, Luca De Trizio, Liberato Manna
Abstract
nanocrystals (NCs). Compared to phosphonic acids with linear alkyl chains, OLPA features a higher solubility in apolar solvents, allowing us to work at lower synthesis temperatures (100 °C), which in turn offer a good control over the NCs size. This can be reduced down to 5.0 nm, giving access to the strong quantum confinement regime. OLPA-based NCs form stable colloidal solutions at very low concentrations (∼1 nM), even when exposed to air. Such stability stems from the high solubility of OLPA in apolar solvents, which enables these molecules to reversibly bind/unbind to/from the NCs, preventing the NCs aggregation/precipitation. Small NCs feature efficient, blue-shifted emission and an ultraslow emission kinetics at cryogenic temperature, in striking difference to the fast decay of larger particles, suggesting that size-related exciton structure and/or trapping-detrapping dynamics determine the thermal equilibrium between coexisting radiative processes.